Do I need to install Git to use Github? If not, then how do I push changes (commits) from the IDE that I use to code? I'm using Visual Studio and Team Foundation to manage the source code.
Fundamentaly, you don't need it if you use Visual Studio >= 2012.
But because you can't do everything with the VS GUI*, and because the GUI is not very good (but improving), that's a very good idea (even perhaps a must) to install the git command line and even a better GUI like GitExtensions.
*: with the GUI, you can't have access to the 'reflog' for example which is one of the first thing that a beginner must understand (with the 'reset' command) to be able to fix every mess he put him into, because he is a beginner ;-) If you master that, it let you try everything and undo and try again until you understand and master every part of git. My second advice is to commit OFTEN because every work committed will never be lost (at worst, recoverable from the reflog).