charging a Rhino 750 3 cell lipo

[Geopache]

hi guys i need help with charging my lipo. it's a Rhino 750 3 cell. i know how to do it but dont know how to find out the mAh and i also find it hard to understand all the discharge rate and something about a C that you have to put in.

please assist i am really excited to get my plane flying.