Download/Install git: http://git-scm.com
Copy MaNGOSR2 source:
git clone git://github.com/mangosR2/mangos.git
git clone git://github.com/mangosR2/scriptdev2.git
For Windows - just run VS project files and compile.
NOTE! MaNGOSR2 officialy don't suppot windows and source can don't compile in VS... Cmake for windows system is not support too =) But you can fix Cmake config files and make patch ;)
More will be later if my brain will not explode =)