Learn French: Apporte ton ordinateur au bureau. - Bring your computer to the office.

This is a special rule for commands (the imperative mood). For regular verbs ending in -er like apporter, you drop the final s in the tu (informal "you") form. So tu apportes (you bring) becomes just apporte (bring!).

How do we know this is the informal "you" since the word tu isn't in the sentence?

There are two clues! First, the verb is in the tu command form. Second, it uses the informal possessive word ton (your). If this were a formal or plural command, you would use the vous form: Apportez votre ordinateur.

Why is it au bureau and not à le bureau?

In French, you can never say à le. When the preposition à (to) meets the masculine word le (the), they always merge together to make au. Since bureau is a masculine word, "to the office" becomes au bureau.

Could I use amène instead of apporte to mean "bring"?

In French, apporter is used when you are bringing an inanimate object that you can carry, like an ordinateur (computer). You use a different verb, amener, when you are bringing a person or an animal.