可以 (kěyǐ) is an auxiliary verb primarily used for expressing permission. It's often translated as "can," but in order to not get it confused with other words, it's best to think of it as "may" to emphasize the permission aspect.
Just put 可以 (kěyǐ) in directly before a verb to create a meaning of "may" (plus the verb). It's the same structure whether it's a statement or a question.
Subj. + 可以 + Verb + Obj.
Use this structure to express permission to do things.
我 可以 进来 吗？Wǒ kěyǐ jìnlái ma?May I come in?
二十 一 岁 以后 可以 喝酒。Èrshí-yī suì yǐhòu kěyǐ hējiǔ.After you are 21 years old, you may drink alcohol.
妈妈，我 可以 出去 玩 吗？Māma, wǒ kěyǐ chūqù wán ma?Mom, may I go out and play?
我们 可以 在 办公室 吃饭 吗？Wǒmen kěyǐ zài bàngōngshì chīfàn ma?Can we eat in the office?
我 可以 在 这里 停车 吗？Wǒ kěyǐ zài zhèlǐ tíngchē ma?Can I park here?