Welcome to the Community. QuickBooks Online is a great program that gives the ability to add or remove users from the account. I'd be glad to provide you with information regarding the users option in QuickBooks.
The program offers the possibility to have more than one user in the account for QuickBooks Online Essentials, Plus and Advanced. Quickbooks Online Easy start includes only one user in the account.
If you're using QuickBooks Easy start, I'd encourage you to upgrade to one of the plans to add new users in the account. You can refer to this article to upgrade your plan.
Let me know if you have any questions, I'll be happy to help.