When you add them as a user the practice and access is determined by you so they will only see what you give them access for.
Here are the steps to add a user to Receivables Manager:
Open ARI Admin
Go to the Users and User Classes tab
Under "User Settings" click the Edit button
As long as the Users are already in PracticeAdmin you will find them in the Users list. You might need to uncheck the box at the bottom of the page "Show only ARI users"
Click on the Users name
Make sure their practice is checked in the box on the right
Click the Edit button at the bottom of the page
Select the User access you want them to have, for example click on "other" button, then check the box for "Office" and check the box for "Patient claims need action"
Make sure the User enabled button is checked
Now click OK
Click OK again on the large screen.