The first thing that you will need to do is create a GitHub account.
On your dashboard, click the “+ New Repository” option, Click “Create Repository”. Now that the repository is created.
you need to get the repository onto your computer. To do this, download and install "Github Deasktop".
Once GitHub Desktop is installed, open it up and sign in to your GitHub account.
choose “Clone repository” where repository is the name of the repository you are looking to clone. GitHub will ask you where to save the clone. Choose a location on your hard drive. you should be able to see your repository on your local machine.
you can either create a new Unity project inside of this folder or you can transfer an existing project into this folder.
Open up the Unity Project that you want to setup for use with GitHub and go to Edit a Project Settings → Editor.
On the right side of Unity, From the “Version Control” drop down box, choose “Visible Meta Files”. From the “Asset Serialization” drop down, choose “Force Text”.
It is important that this is done. If you do not do this, your GitHub commits and pulls will NOT work. Once this step is done, you can begin to commit and pull changes to your GitHub repository and everything should work.
Transfer From Mark Philipp, Application Engineer at Studica.