We've all been there, us traditionally windows developers. Occasionally a tool on windows will open Vi, typically when you've not configured git, or you're trying out Linux and experimenting with .NET cross platform.
First - hit esc a few times to make sure you are in Command Mode. Then you want to enter
This will abandon all changes and quit. If you do want to save your changes, the way to quit is still press esc to get into Command mode and then :