This is a repost of an answer I wrote on Stack Overflow.
GitLab is a git repository site similar to GitHub.
1. Create a new project on GitLab
Chose the +
button on the menu bar. Add a project name and then click "Create project".
This will give you a new project address. Choose the https version.
It will look something like this:
https://gitlab.com/MyUserName/my-project.git
2. Create a Git repository in Android Studio
In the Android Studio menu go to VCS > Import into Version Control > Create Git Repository…
Select the root directory of your project. (It will be automatically selected if you already have it highlighted in the Project view. Otherwise you will have to browse up to find it.)
3. Add remote
Go to VCS > Git > Remotes…. Then paste in the https address you got from GitLab in step one.