Antes de enviares o documento, clica no ícone certo.

Antes de means before.

In Portuguese, when before is followed by a verb, you normally use antes de + infinitive:

• antes de sair = before leaving / before you leave
• antes de comer = before eating / before you eat

So Antes de enviares o documento means Before you send the document.

Because this sentence uses the personal infinitive.

After antes de, Portuguese can use an infinitive. If the subject is a specific person, especially in European Portuguese, the infinitive can show who that subject is:

• enviar = to send
• enviares = for you to send, with tu

So antes de enviares makes it clear that the sentence is talking to you in the informal singular.

Here, no. Here it is the personal infinitive.

It looks identical to the tu form of the future subjunctive, but the structure tells you what it is. After the preposition de, Portuguese uses an infinitive, not a subjunctive form.

So in:

• Antes de enviares o documento

the word enviares is understood as a personal infinitive because it comes after de.

Clica is the affirmative imperative for tu.

• tu clicas = you click
• clica = click

So the sentence is giving a direct instruction to one person informally.

Clique would be the more formal imperative, used with você, o senhor, a senhora, etc.

Compare:

• Clica no ícone certo. = Click the right icon. informal, tu
• Clique no ícone certo. = Click the right icon. formal

Yes, but that is normal.

Portuguese often leaves out subject pronouns because the verb form already shows who the subject is. Here, both verbs point to tu:

• enviares = you send, informal singular
• clica = click, informal singular command

You could say Antes de tu enviares o documento..., but it is usually unnecessary and less natural here.

No is a contraction of em + o.

• em = in / on
• o = the
• no = in the / on the

With clicar, Portuguese commonly uses clicar em. So:

• clica no ícone = click on the icon

Because Portuguese uses definite articles more often than English.

In this sentence, the speaker means a specific document and a specific icon, so o sounds natural:

• o documento = the document
• o ícone = the icon

English sometimes drops articles where Portuguese keeps them, but in Portuguese this kind of instruction normally uses them.

Here certo means right or correct.

• o ícone certo = the right icon / the correct icon

It comes after the noun because that is the normal position for this meaning.

This matters because certo before the noun can mean something different:

• o ícone certo = the correct icon
• certo ícone = a certain icon

So in this sentence, ícone certo is the natural choice.

Yes. That is grammatically correct.

• Antes de enviar o documento = before sending the document / before you send the document
• Antes de enviares o documento = before you send the document, specifically with tu

The version with enviares is more explicit about the subject and is very natural in European Portuguese when speaking directly to tu.

Yes, it sounds very European Portuguese.

The combination of:

• enviares
• clica

shows informal tu very clearly, and that is especially typical in Portugal.

In standard Brazilian Portuguese, a more common version would be:

• Antes de enviar o documento, clique no ícone certo.

That uses the more common Brazilian instruction style with você-type forms.