Learn Hardcore Malay: Ibu menampal gambar pelangi di papan putih. - Mother sticks a picture of a rainbow on the whiteboard.

The verb menampal already carries the idea of “to stick/paste”, so you don’t add anything like adalah or ialah.
Words like adalah/ialah are used in equational sentences (A = B), e.g. Dia adalah doktor (“He/She is a doctor”), not with normal action verbs.

How do we know if menampal is present, past, or future tense?

Malay verbs are not marked for tense the way English verbs are. Menampal itself is “to paste/stick”, with no built-in time.

The time is understood from context or from time words:

Ibu menampal gambar pelangi di papan putih.
Could be “Mother is sticking / sticks / stuck a picture of a rainbow on the whiteboard” depending on context.
To make it clearly past:
Tadi ibu menampal gambar pelangi di papan putih.
(“Earlier, mother stuck…”)
To make it clearly future:
Nanti ibu akan menampal gambar pelangi di papan putih.
(“Later, mother will stick…”)

So menampal itself doesn’t change form for tense.

What is the difference between tampal and menampal?

Tampal is the root verb (“paste”, “stick on”), and menampal is the meN- prefixed form, which is the usual way to form an active verb in standard Malay.

tampal – root; can be used as a command or in informal speech:
- Tampal gambar itu di sini. (“Paste that picture here.”)
menampal – sounds more standard and is used in normal sentences:
- Ibu menampal gambar pelangi…

In casual conversation, you will hear both, but in formal or written Malay, menampal is preferred in a full sentence with a subject.

What exactly does Ibu mean here? Is it “mother”, “my mother”, or something else?

Ibu literally means “mother”, but in many contexts it is understood as “my mother” when the speaker is talking about their own mother.

So:

Ibu menampal gambar pelangi…
Most naturally: “Mum/Mother is sticking a picture of a rainbow…”

Other notes:

Ibu can also be used as a polite form of address to an older woman (similar to “Madam”), depending on context.
More colloquial words for “mum” in Malay are Mak, Emak, Mama, etc., but Ibu is neutral and polite.

How should I understand the phrase gambar pelangi? Is it “rainbow picture” or “picture of a rainbow”?

In Malay, noun + noun often means “X of Y” or a compound noun.

gambar = picture
pelangi = rainbow
gambar pelangi = a picture of a rainbow / rainbow picture

This structure is very common:

gambar kucing – a picture of a cat
buku cerita – story book
kereta polis – police car

So gambar pelangi is “picture of a rainbow” (no extra word like “of” is needed).

Why is there no word for “a” or “the” in this sentence?

Malay does not have articles like English “a”, “an”, “the”.
Gambar pelangi can mean:

“a picture of a rainbow”
“the picture of the rainbow”

The exact meaning depends on context. If you need to be more specific, you can add other words:

sebuah gambar pelangi – one (a) picture of a rainbow (using a classifier)
gambar pelangi itu – that particular rainbow picture / the rainbow picture (using itu “that”)
gambar pelangi ini – this rainbow picture (using ini “this”)

What does di mean in di papan putih? Is it “in”, “on” or “at”?

Di is a general preposition of location. Its exact English translation depends on the noun:

di rumah – at home
di dalam kotak – in the box
di meja – at the table / on the table

In di papan putih:

papan putih = whiteboard
di papan putih therefore is most naturally “on the whiteboard” in English (because that’s how English talks about things attached to boards).

Malay doesn’t need to distinguish “on/at/in” as strictly as English does; di just means “at (the location of) …”.

Does papan putih literally mean “white board”? Is it always a classroom whiteboard?

Literally:

papan = board / plank
putih = white
papan putih = white board

In modern usage, papan putih is commonly understood as a whiteboard used for writing with markers, especially in classrooms and offices.

However, in a different context, it could also mean any board that is white (a literal white piece of board). Usually, the context (classroom, teaching, office, etc.) makes it clear you mean a whiteboard.

Can we change the word order and say “Ibu di papan putih menampal gambar pelangi”?

That sentence is grammatical, but the focus changes slightly and it sounds less neutral.

Ibu menampal gambar pelangi di papan putih.
Neutral: “Mother is sticking a picture of a rainbow on the whiteboard.”
Ibu di papan putih menampal gambar pelangi.
Feels like: “The mother who is at the whiteboard is sticking a picture of a rainbow.”
(It sounds like “the mother at the whiteboard…”, describing which mother you mean.)

The original order (verb and object first, then place) is the most natural for a simple sentence describing what someone is doing and where.

Is gambar singular or plural here? How do you say “pictures of rainbows”?

Malay usually does not mark plural with an -s like English.
Gambar can be singular or plural, depending on context.

In this sentence, with no extra markers, we usually understand:

gambar pelangi – “a picture of a rainbow” (or just “a rainbow picture”)

To make it clearly plural, you have options:

banyak gambar pelangi – many pictures of rainbows
gambar-gambar pelangi – pictures of rainbows (reduplication often shows plurality)
beberapa gambar pelangi – several pictures of rainbows

So plural is shown by context, reduplication, or quantity words, not by changing the noun’s ending.

Is menampal the only verb I can use for “sticking” something on a board?

No; Malay has a few verbs that can work, with slightly different nuances:

menampal – to paste/stick (often using glue, tape, etc.). Very suitable here.
melekatkan – to make something stick/adhere:
- Ibu melekatkan gambar pelangi di papan putih.
menyematkan – to pin (using a pin, clip, etc.)
menampal poster / melekatkan poster – both common for “putting up a poster”.

In everyday usage, for sticking paper on a wall/board using tape or glue, menampal and melekatkan are both natural. In your sentence, menampal is perfectly appropriate and common.