Push the pistons back into the caliper with a lever while the disc is still in situ and keep an eye on the opposing pistons or they will pop out! It's not quite as easy then. As the rest have said, 2 bolts for the caliper then the disc slides off, it may however be retained by a small screw so just losen this and off it wil pop. If you're scared at the prospect of the pistons popping out of the caliper you can buy a piston spreader tool from sealey for about £20. This decice pushes both pairs of pistons back simultaneously. Hope this helps.