Permission Sets Assignment
You will have 3 permissions sets:
Tuvis Admin - Provides access to Tuvis setup pages, where you can change your accounts settings. And to the Dashboard.
Tuvis Sales User - It will give access to Opportunities inside Tuvis Agent Panel.
Tuvis Services User - It will give access to Cases inside Tuvis Agent Panel.
(If the user should have access to Opportunities and Cases, you need to assign both permissions)
How to set these permissions:
In SalesForce, go to Setup, search for Permission Sets
Open the permission set you want, click on Manage Assignments
Click on Add Assignments, and select the users you want. Then click on Assign.
You can also see a step by step in this video