Yeah thats what I hate about RTR's you don't know how to build them. You really gotta learn because your car is going to be repairs more than you'll be running it most likely. Its really not tht hard

Anyway to fix the brakes try screwing in the plastic screw with your fingers in and ever 5 twists or so (with it on neutral) check and see if there is any brake drag when you move the car forward. When you get to this point unscrew it one or two twists at a time until there is no brake drag at neutral. This way as soon as you touch the brakes they will engage. Hope it works.

Another thing, make sure the screws that go into the transmittion case and hold in the brake "pads (the metal ones)" are all the way screwed in, if it isn't then the brakes are useless.