How do you release a locked emergency brake on a Chevy S10 pickup when the brake handle will not release?

I am assuming that you can physically move the parking brake lever however the actual parking brake mechanism will not release. If that is the situation, then first, block the wheels with a large piece of wood, brick, or something substantial to prevent the vehicle from rolling for safety sake. Then place the parking brake lever in the released position or have someone hold the parking brake lever in the released position while you or someone crawl under the vehicle and try pulling and wiggling the parking brake cables to see if you can get them to release. Sometimes rust will prevent the cables from releasing properly and some movement of the cables is all it takes to release them. If this didn't work then either your cables are too rusted/damaged to release or there is something else wrong with the parking brake mechanism which will require someone experienced and qualified to work on brakes to diagnose and repair. This leaves you with only one option which is to have the vehicle towed someplace to have it fixed.