1) Grab the OSX or Windows installer from the downloads page. Linux binary available too.
3) Dump your samples and other files you want to load in /Users/<your_user_name>/vMPC/Stores/MPC2000XL. This is also where anything you save will be stored.
Warning: Files in that directory are name-mangled by the emulator just like on the real 2000XL! This means you shouldn't put the only copy of some important files there. Your data might become corrupted.
4) Report bugs and feature requests here.
MPC® and Akai Professional® are a registered trademarks of inMusic Brands. Inc. This emulator is not affiliated with inMusic and use of the MPC® and Akai Professional® names has not been authorized, sponsored or otherwise approved by inMusic.