Question

how to use can or could ?

Answer 1

can is used when it is in present tense and code is used when it is in past tense

Answer 2

When could is used as the past tense of can, it refers to an ability that a person generally had in the past or to something that was generally possible in the past ("When I was younger, Icould run for miles," or "It used to be you could buy lunch for a dollar.").