Ég verð rugluð þegar leiðbeiningarnar eru ekki nógu skýrar.

Because verða means to become / to get, while vera means to be.

So:

• Ég er rugluð = I am confused
• Ég verð rugluð = I get/become confused

In this sentence, the idea is that the unclear instructions cause a change of state: the speaker becomes confused.

Verð is the 1st person singular present tense of verða.

So:

• ég verð = I become / I get
• þú verður = you become
• hann/hún/það verður = he/she/it becomes

It matches the subject ég.

Not usually. Ruglaður is an adjective meaning confused, and it changes for gender and number.

For singular:

• masculine: ruglaður
• feminine: rugluð
• neuter: ruglað

So if the speaker is female, Ég verð rugluð is correct.
A male speaker would normally say Ég verð ruglaður.

In sentences like this, learners can think of it as an adjective meaning confused / mixed up. Historically it is related to the verb rugla (to confuse / to mix up), but in everyday use here it functions like an adjective describing the speaker’s state.

So verða + adjective is a very useful pattern:

• verða þreyttur/þreytt = get tired
• verða reiður/reið = get angry
• verða ruglaður/rugluð = get confused

Here þegar means when and introduces a time clause:

• þegar leiðbeiningarnar eru ekki nógu skýrar
  = when the instructions are not clear enough

In this kind of sentence, it often has a general sense similar to whenever.

Also note: þegar can mean already in other contexts, but not in this sentence.

It is the noun leiðbeining with plural and definite marking added.

A useful breakdown is:

• leiðbeining = instruction / direction
• leiðbeiningar = instructions
• leiðbeiningarnar = the instructions

Icelandic usually puts the on the end of the noun as a suffix, instead of using a separate word like English the.

Because leiðbeiningarnar is plural, so the verb vera (to be) must also be plural.

Compare:

• Leiðbeiningin er skýr. = The instruction is clear.
• Leiðbeiningarnar eru skýrar. = The instructions are clear.

So eru is simply the plural present form: are.

Because the adjective must agree with leiðbeiningarnar.

The noun leiðbeining(ar) is feminine, and here it is plural, so the adjective skýr (clear) appears in the feminine plural form skýrar.

Compare:

• leiðbeiningin er skýr = the instruction is clear
• leiðbeiningarnar eru skýrar = the instructions are clear

This agreement happens even though the adjective comes after the verb.

Nógu means enough / sufficiently.

So:

• skýrar = clear
• nógu skýrar = clear enough
• ekki nógu skýrar = not clear enough

It is a very common word in Icelandic for expressing that something reaches, or does not reach, a sufficient level.

Because in normal Icelandic clause structure, the finite verb usually comes before ekki.

So Icelandic says:

• leiðbeiningarnar eru ekki nógu skýrar

not:

• leiðbeiningarnar ekki eru ...

This is a common pattern to get used to:

• Hún er ekki hér. = She is not here.
• Ég skil ekki. = I do not understand.
• Þau koma ekki. = They are not coming.

Yes. You can also say:

• Þegar leiðbeiningarnar eru ekki nógu skýrar, verð ég rugluð.

That means the same thing.

The important thing to notice is the word order in the main clause: after the fronted þegar-clause, Icelandic keeps the verb early, so you get verð ég, not ég verð. This is part of normal Icelandic verb-second word order.

Very often, yes. Icelandic commonly uses leiðbeiningar in the plural for instructions / directions, much like English does.

But the singular leiðbeining also exists and can be used when you mean one instruction or a single piece of guidance.