To install GitKraken Client download the correct binary for your system.
Then follow the installation instructions provided on their website.
In the installation instructions you’ll see that you do not actually need to install Git separately to use GitKraken Client as it ships it’s own Git framework, NodeGit, which is primarily developed and maintained by members of the GitKraken development team.
In order to effectively work with GitHub repositories through GitKraken Client, you will need to enable the integration and authenticate with GitHub. You can then use GitKraken Client to define or generate an SSH key that authenticates git operations on GitHub through GitKraken Client. Follow the instructions on the GitKraken site to perform both steps.