Loosen the 2 screws/nuts that don't have wires going to them, and pull off toward non drive end of starter. If starter is still on engine this may be VERY difficult. With starter off it will be easy to se that there are 2 screws attaching it that don't have wires on them. I think they take an e-torx 6 lobe star socket on most of them. They will be pretty tight. once you have these long screws loos they solenoid should pull off. The plunger on most of these starters is slipped into a groove in the engage lever.
Good luck, hope this helps.