I just purchased a acadia with no key need to purchase a key how much and how do i do that

You should have recieved 2 fobs w purchase that's the key

Go back to the dealer and let your sell person know you need another fob. They will take care of it. This way you know it will done right.

Key fobs are like 300 and then you have to have a dealer or locksmith with the right tools program it for your car and that's like $85 so you're looking at like around 400 not cheap that's why I got the key fob replacement well worth it

Most cars do not need a key. They start with a start and stop button on the dash. Doors lock and unlock with the fob.