Most Linux Distro's include this in their Repositories. How you install Software from the Repo's depends on the Distro.
On Debian based Distro's (Debian, Ubuntu etc.), you can open a terminal and enter:
sudo apt update sudo apt install git-hub
If you are using a GUI in your Distro, there is probably also a package Manager installed, like Synaptic, and then you can open that & search for git-hub, select it & install it...
Once git is installed, you can use it for working with any Git Repository including GitHub. There are other Git Hosting providers like Bitbucket, Gitlab, etc...
On Debian based Distro's (Debian, Ubuntu etc.), you can open a terminal and enter:
sudo apt update
sudo apt install git-hub
If you are using a GUI in your Distro, there is probably also a package Manager installed, like Synaptic, and then you can open that & search for git-hub, select it & install it...