I understand why I can't add any members since we already have 10 people but one person we added quit as we added them and I cannot figure out how to remove them. I was the one who set up the Jira but I don't have the user settings shown in the docs to add or remove people. I've spent over an hour on this so I would really appreciate some help.
it sounds that you are lacking administrator permissions to do the desired maintenance.
Please try navigating to http://admin.atlassian.com and report back what the result is.
From your description you should be enabled access there so you can manage your users as you wish. If you are getting an "access denied" error back you definitely lost (somehow?) administrator privileges.
Please also refer to the documentation for a better understanding of the several permissions used in Cloud:
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