Lift the keyboard slightly until you see the cable connection the keyboard to the rest of the computer

Most of the time, these connectors will have a lip or a tab along the top that can be used to push the connector out of its socket.

To disconnect, use the wide end of a spudger to push on the connector tab to slide it out of its socket.

It may take a lot of force to disconnect the cable. Go slowly, and don't pull on the cables.