Use o cinto antes de sair da garagem.

Because this is a command, and use is the normal affirmative imperative form for você.

• usar = to use / to wear
• você usa = you use / you wear
• Use! = Use/Wear! (command to você)

In Brazil, commands with você are very common and sound natural in instructions, notices, and advice. So Use o cinto is like saying Wear the seat belt or Use the seat belt.

If you were speaking to someone with tu, the textbook imperative would be usa:

• Usa o cinto.

It is neutral to polite, not overly formal. In Brazilian Portuguese, você forms are widely used in everyday speech, public signs, instructions, and customer-facing language.

So Use o cinto works well for:

• a sign
• a safety instruction
• advice
• a direct but normal command

It does not sound stiff in the way some English imperatives can.

By itself, cinto literally means belt. But in a driving context, o cinto is usually understood as seat belt.

If you want to be extra explicit, you can say:

• cinto de segurança = seat belt

So:

• Use o cinto = Wear the belt / Use the seat belt
• Use o cinto de segurança = Wear the seat belt

In this sentence, because of garagem and the driving context, learners should understand it as seat belt.

Portuguese uses definite articles much more often than English does. So o cinto is the natural way to say the belt / the seat belt here.

• Use o cinto sounds normal and complete.
• Use cinto can sound more like a general slogan or label, and is less natural in ordinary speech.

English often says Wear a seat belt or Wear your seat belt, but Portuguese frequently prefers the article:

• Use o cinto
• Feche a porta
• Lave as mãos

Antes de means before, and after it Portuguese often uses an infinitive.

So:

• antes de sair = before leaving / before going out

This structure is very common:

• antes de comer = before eating
• antes de dormir = before sleeping
• antes de entrar = before entering

Here, sair stays in the infinitive because the subject is general or understood from context.

Because the verb sair normally goes with the preposition de when you say where someone is leaving from.

• sair de casa = leave home
• sair do carro = get out of the car
• sair da garagem = leave the garage / drive out of the garage

So de is required by the verb here.

Because de + a contracts to da in Portuguese.

So:

• de + a garagem → da garagem

This kind of contraction is extremely common:

• de + o = do
• de + a = da
• em + o = no
• em + a = na

So sair da garagem is just the normal contracted form of sair de a garagem.

Portuguese often leaves out subject pronouns when they are already clear from the verb form or the situation.

So instead of saying:

• Você use o cinto ❌

Portuguese simply says:

• Use o cinto ✅

In commands, omitting the pronoun is especially normal. The sentence naturally means (You) wear the seat belt before leaving the garage.

Yes. Those are possible alternatives, but the nuance changes a little.

• Use o cinto = wear/use the seat belt
• Coloque o cinto = put on the seat belt
• Afivele o cinto = fasten/buckle the seat belt

So Use o cinto is a general instruction, while afivele o cinto is more specific about buckling it.

In real-life Brazilian Portuguese, afivele o cinto and coloque o cinto de segurança are also very common in safety contexts.

Yes. It is feminine:

• a garagem
• da garagem
• na garagem

That is why the contraction is da and not do.

A rough pronunciation for an English speaker is:

• Use ≈ OO-zee
• o ≈ a quick oo
• cinto ≈ SEEN-too, but with a nasal sound in the first syllable

A more natural Brazilian flow would sound something like:

OO-zee u SEEN-too

A couple of useful notes:

• The s in use sounds like z.
• The final e in use is usually pronounced like ee in Brazilian Portuguese.
• The in in cinto is nasal, so it is not exactly the English seen.

Yes, grammatically it can. Sair da garagem simply means to leave the garage / go out of the garage.

The exact image depends on context:

• a person walking out
• a car backing out
• someone driving out

Because the sentence talks about o cinto, the intended meaning is clearly about a car and a seat belt. So in context, it means something like before driving out of the garage.