G clamp or crossed large screw drivers but dont slip , I think there is a factory tool..
sorry but that's very bad advice as using a G clamp or leavers will break something.
The rear pistons screw in and its best to use a brake piston toll (ABW for Fords is best although at a pinch you can use a universal cube type). Note they screw different directions LH piston clockwise RH piston anticlockwise.
Spray the piston boots with WD40 or similar first so the don't tear them when screwing them in then screw in until they bottom and then until the notch on the piston lines up with the nipple on the new pads.