I have created a map that users can add themselves to. I would suggest only giving city/state information. You can add your username in the description field as an option.
https://drive.google.com/open?id=13vPfjU...sp=sharing
I have added groups by continent.
Step 1, type your city and state in the search box and select the correct result.
Step 2, click "ADD to MAP"
Step 3, click the edit button
Step 4, add username to name field and anything you feel important to the description field. Then, click save.
Step 5, verify it added to the correct continent and shows on the map correctly.