أستعمل هذا البرنامج في المكتب كل يوم.

أستعمل means I use. The initial أـ is the marker for first person singular in the present/imperfect tense, so the subject is already built into the verb.

So:

• أستعمل = I use
• تستعمل = you use / she uses (depending on context)
• يستعمل = he uses
• نستعمل = we use

Because of that, Arabic does not need a separate word for I here.

Because Arabic verbs already show the subject.

In أستعمل, the أـ tells you the subject is I, so adding أنا is usually unnecessary.

You can say أنا أستعمل هذا البرنامج..., but that usually adds emphasis, like:

• I use this program...
• As for me, I use this program...

Without أنا, the sentence sounds neutral and natural.

It can do both.

In this sentence, أستعمل is in the imperfect form, which commonly expresses:

• a present action: I am using
• a general/habitual action: I use
• a repeated action: I use ... every day

Because the sentence also has كل يوم (every day), the meaning is clearly habitual: I use this program every day.

If you wanted the future, you would normally add سـ or سوف:

• سأستعمل هذا البرنامج = I will use this program
• سوف أستعمل هذا البرنامج = I will use this program

This is normal in Arabic.

In English, we say this program. In Arabic, the usual pattern is:

• هذا + definite noun
• هذه + definite noun

So:

• هذا البرنامج = this program
• هذه السيارة = this car

The noun usually takes الـ after a demonstrative in standard Arabic. So هذا البرنامج is the expected form, not هذا برنامج in normal MSA usage.

Because that is the normal Arabic order for demonstratives in MSA.

Arabic says:

• هذا البرنامج = literally this the-program
• هذه الكلمة = this the-word

So unlike English, the demonstrative comes first, and the noun after it is usually definite.

It is the direct object of the verb أستعمل.

The structure is:

• أستعمل = I use
• هذا البرنامج = this program

So the sentence means: I use this program...

If you fully showed case endings, the noun البرنامج would be in the accusative because it is the direct object:

• أستعملُ هذا البرنامجَ

The word هذا itself does not visibly change here, but the noun after it shows the case.

في is the preposition meaning in.

So:

• في المكتب = in the office

Like other Arabic prepositions, في makes the following noun genitive, so in fully vocalized Arabic you would have:

• في المكتبِ

المكتب means the office.

Arabic often uses the definite article الـ when referring to a specific or understood place. So في المكتب naturally means:

• in the office
• sometimes, depending on context, at the office

If you said في مكتب, that would mean in an office.

That is a very natural place for a time expression in Arabic.

The sentence is arranged like this:

• أستعمل هذا البرنامج = I use this program
• في المكتب = in the office
• كل يوم = every day

Arabic word order is flexible, so كل يوم can move, but at the end it sounds very normal and straightforward.

For example, these are also possible:

• أستعمل هذا البرنامج كل يوم في المكتب
• كل يوم أستعمل هذا البرنامج في المكتب

The original sentence is simply one common, natural ordering.

كل means every or all, depending on context.

So:

• كل يوم = every day
• كل أسبوع = every week
• كل سنة = every year

Grammatically, كل is followed by a noun in an iḍāfa construction:

• كلَّ يومٍ

Here:

• كلَّ is in the accusative because it functions as an adverbial expression of time
• يومٍ is genitive because it is the second part of the iḍāfa

In normal unvocalized writing, you just see كل يوم.

Yes. Both are possible.

• كل يوم = every day
• يوميًا = daily

So you could say:

• أستعمل هذا البرنامج في المكتب يوميًا

That means essentially the same thing.
كل يوم is very transparent and common for learners, while يوميًا is a little more compact and adverb-like.

In fully vocalized MSA, it would be:

أستعملُ هذا البرنامجَ في المكتبِ كلَّ يومٍ

Here is why:

• أستعملُ: final ـُ because the verb is in the indicative
• هذا البرنامجَ: the phrase is the direct object, so البرنامجَ is accusative
• في المكتبِ: after في, the noun is genitive
• كلَّ يومٍ: كلَّ is accusative as an adverbial expression, and يومٍ is genitive in iḍāfa

In everyday printed Arabic, these endings are usually not written.

No. Another very common verb is أستخدم.

So both of these are natural:

• أستعمل هذا البرنامج = I use this program
• أستخدم هذا البرنامج = I use this program

Both are correct and common in Modern Standard Arabic.
Sometimes one may sound more natural in a specific context, but for most learners, both are worth knowing.