You can do this from the Team Explorer tab, see:
Git - Git in Visual Studio[
^]
But normally VS should connect automatically.
Although Visual Studio 2019 has good Git support by now you might prefer to use another tool, see:
best-git-clients-for-windows[
^]
If you want to use Git from the command line, you can use
Git Bash by right clicking the folder in Explorer, see:
Git for Windows[
^]