How to manage login/tokens on clients

I am a relatively new user to git and gitlab, a software contractor. I have a standard free account, several individual projects, and a group I created for one of my clients with two projects in it. So far, I am the only user for this group, though I’d like to add more users eventually.

I have been using Source tree, but trying to learn to use the command line.

I have used a mix of site logins, ssh keys, and tokens. I have only been successful with tokens through Source tree, but would like to learn to use them on the command line.

I have a couple situations…

  1. I have a repo that is set up and working, but i’d like to move it to use a project token. I’m not sure what credentials it’s using for gitlab at the moment.

  2. I have a repo that was copied from another machine that was set up with a remote gitlab project. But now it’s not linked to gitlab, and it’s one commit ahead. How do I specify the gitlab project as a remote using a project deploy token?

  3. are group tokens available with my free account? I saw you need to set up a rails install to call the API to generate one. But thst seems like a perfect solution as these systems are shared lab computers, and the code is edited by several people.