My rear break lights don't work how can I fix or.

Check your brake light bulbs. They could both be blown. If they are OK, have a look at the brake pedal. See if a switch is attached to it.
If yes, check if the switch has power at one of the wires. If it has power on one of the wires, disconnect the switch and touch a metal paper clip
cross the 2 connectors (if it has more than 2 wires, you need to check a wiring diagram first). Do the lights come on now?

Thomas

Check fuse and check power at and through brake light switch when depressed, if ok, check globes, start here.