يملأ الوصي الاستمارة ويوقعها اليوم.

A careful MSA reading is:

yamlaʾu al-waṣiyyu al-istimārata wa-yuwaqqiʿuhā al-yawma

A simpler pause-style reading, without full case endings, is often closer to:

yamlaʾ al-waṣī al-istimāra wa-yuwaqqiʿhā al-yawm

A few pronunciation points:

• يملأ = yamlaʾ: the last sound is a hamza, a glottal stop.
• الوصي = al-waṣī in pause, but formally al-waṣiyyu with case ending.
• يوقعها here is understood as yuwaqqiʿuhā (he signs it), with a doubled middle consonant in the underlying form.
• ها = hā = it.

Because Arabic very commonly uses verb–subject–object order, especially in formal written language.

So:

• يملأ = fills
• الوصي = the guardian
• الاستمارة = the form

Literally, the structure is:

fills the guardian the form

That sounds odd in English, but it is normal in Arabic.

You could also say:

الوصي يملأ الاستمارة ويوقعها اليوم

That version starts with the subject and is also correct. It gives slightly more focus to the guardian.

الوصي is the subject of the first verb يملأ and also of the second verb يوقعها.

In full grammatical terms, it is:

• a definite noun
• in the nominative case
• meaning something like the guardian / the trustee / the legal custodian, depending on context

In fully marked Arabic, it would be read as الوصيُّ or more precisely الوصيُّ/الوصيّ depending on how fully you vocalize the word.

Because the verb comes from the root م ل أ, whose last radical is a hamza.

The past tense is:

• ملأ = he filled

So the present/imperfect is:

• يملأ = he fills / is filling

The hamza is part of the root, so it stays in the spelling.

This is why the word is not pronounced like yamla, but yamlaʾ.

They are in the imperfect form, which in Arabic can cover several meanings depending on context:

• present: fills / is filling
• habitual: fills (regularly)
• sometimes future, if another word makes that clear

In this sentence, اليوم (today) makes the time reference clear, so the natural meaning is present/current:

The guardian fills out the form and signs it today.

ها is an attached object pronoun meaning it.

So:

• يوقع = he signs
• يوقعها = he signs it

Arabic often attaches object pronouns directly to verbs instead of using a separate word.

This is extremely common:

• كتبها = he wrote it
• قرأها = he read it
• وقّعها = he signed it

Because it refers to الاستمارة, and استمارة is a feminine singular noun.

In Arabic, pronouns agree with the noun they refer to.

So:

• الاستمارة = feminine singular
• therefore it must be ها

If the noun were masculine singular, you would usually use ـه instead.

Good question. The meaning here comes from a different verb form.

• وَقَعَ (Form I) can mean fell or happened
• وَقَّعَ (Form II) means signed

In normal unvowelled writing, the shadda is often not written, so يوقع can represent يُوَقِّعُ in context.

So here the sentence is understood as:

• يُوَقِّعُها = he signs it

not

• يُوقِعُها = something like he causes it to fall / inflicts it, depending on context

The meaning of the sentence makes signs it the only natural reading.

الاستمارة is the direct object of يملأ.

It is the thing being filled out.

So the structure is:

• يملأ = verb
• الوصي = subject
• الاستمارة = direct object

Then the second verb refers back to that same object with ها:

• ويوقعها = and signs it

In full case marking, الاستمارة would be in the accusative:

• الاستمارةَ

Yes, literally اليوم is the day, but in standard usage it very often means today.

This is a normal Arabic expression.

So in sentences like this:

• اليوم = today

It functions as an adverb of time.

In full grammatical reading, it is often treated as an adverbial accusative:

• اليومَ

Arabic word order is flexible, and adverbs of time often come near the end.

So:

يملأ الوصي الاستمارة ويوقعها اليوم

is a very natural order.

But other orders are also possible, for example:

• اليوم يملأ الوصي الاستمارة ويوقعها
• يملأ الوصي اليوم الاستمارة ويوقعها

The difference is mostly one of emphasis or style, not core meaning.

Because both nouns are definite here.

• الوصي = the guardian
• الاستمارة = the form

Arabic uses الـ to mark definiteness, similar to the in English.

If they were indefinite, they would be:

• وصيّ = a guardian
• استمارة = a form

In real usage, Arabic may use definiteness a bit differently from English, but here the definite reading is straightforward.

A fully marked version can be given as:

يَمْلَأُ الوَصِيُّ الِاسْتِمَارَةَ وَيُوَقِّعُهَا اليَوْمَ

This shows:

• يَمْلَأُ = verb in the imperfect
• الوَصِيُّ = nominative subject
• الِاسْتِمَارَةَ = accusative direct object
• يُوَقِّعُهَا = second verb + attached object pronoun
• اليَوْمَ = adverb of time

In everyday printed Arabic, many of these vowel marks are omitted, and readers rely on grammar and context.