On both ends, there are two bolts with the torx heads. Those are pretty big.
Once you've got them, what may happen is the pads eat into the rotor and won't come past the lips.
For fronts, use a big screwdriver to pry the pads away from the rotor. You want to push the piston back into the caliper, anyways.
For the rear, make sure the parking brake is off. If the rotor is too worn it's a problem as the parking brake mechanism advances the pads as they wear. It this case you've got to force the calipers off. Tapping with large hammer works.
Retracting the rears requires turning the piston whilst it gets pressed back. There are tools for that. Some people can manage with needle-nose pliers or twisting the piston with a large pliers.
It's a typical counter clockwise turn to loosen it but can require an awful lot of torque to remove it- channel your inner lumberjack strength after using a bit of penetrating oil and letting it sit for a while, and perhaps 'shock' it with a heavy hammer. A decade of rust and salt can make them pretty tough to get started.