Its better to install Git from its Official package repo , its very easy but sometimes you may not get the latest version.
On the terminal, type in the command:
sudo apt-get install git-core
If you need gitk, type in command:
sudo apt-get install gitk
One more important tool is git gui , it provides user interface for staging , commit , push etc features.
just type command to install git-gui
sudo apt-get install git-gui
type git gui command in the git repo to see the changed files and perform most of the operations that's otherwise difficult without GUI.
Some important git tutorials:
follow michael's Git tutorial on youtube for basic understanding of Git:
Ep1 part1: http://www.youtube.com/watch?v=HaSDIdNkCDQ
go through all the parts and episodes.