You are creating a new user and want to associate this user with an existing client:

1. Open https://portal.onestopreporting.com/ and log on with your tenanthost administration user (provided by OneStop Reporting)
2. After you have created the new user (https://help.onestopreporting.com/faq/tenanthost/how-do-i-create-new-users-in-a-tenanthost/), go to Clients.
3. Go to Settings – Administration – click the Users tab.
4. Click the user name.
5. In the menu that appears under the user, you can manage the user’s role, permissions, data access and module access

For more information see Set permissions and data access for a user