Bmx Pain The Chain On My Bmx Keeps Slipping, How Do I Stop This From Happening?

The chain on my bmx keeps slipping, how do i stop this from happening? - bmx pain

Not long ago, I bought a new pink "BMX Rhino" Toys R 'Us, the chain gets stuck and the wheels do not turn around when the pedal, or sometimes I can not stop kicking, and I need to move your feet with the wheels. It is a pain in the ***
Any idea how to solve this problem?
This is a new bike, but it used to pay, so ideally do not want to spend money to make repairs. It costs a lot?