That light goes off for 2 things: Low brake fluid, & the handbrake lever.

1) Check your brake fluid level. If it's not low, then unplug the 2 wires coming from the brake fluid reservoir. If that fixes the light, then you've got a screwed-up float switch in the reservoir cap.

2) Check the little switch under the handbrake lever. Maybe it's bent or something, so it doesn't get pressed down when the handbrake lever is down. You probably have to dismantle the console to see it.