How to disengage brake in troy built riding lawn mower?

I don't know exactly what model you have. But, generally the brake is on the transaxle (rearend) just inside the right rear wheel. There is a rod with a spring going to an arm there. This arm rotates and pushes two small pin against a plate the comes out of the transaxle to stop it. Many times these small pins get corroded. They are metal and the transaxles and usually aluminum. You will have to take them out and sand the corrosion of, lubricate them and reinstall them. It's not a hard job. It just takes a half hour or so. I ran a riding mower for months with no brakes because I couldn't figure it out.