Hi @Alan_c, welcome to the community.
You can manage Atlas Users by clicking on the Database Access link in the sidebar under the security section.
After clicking on the link, you would see an interface like this:
Also, we have already discussed this question in our FAQ post, please take a look at question no. 6 for more information.
In case you have any doubts, please feel free to reach out to us.
Thanks and Regards.
Sourabh Bagrecha,
Curriculum Services Engineer