To add Row Level Security, Follow the below steps:
1. Go to the Modelling ribbon and click on Manage Roles.
2. You will see a dialog box to add Roles and manage roles.
3. Click on Create and enter the details, and optional DAX expression to filter the required data.
4. Click on Save.
5. To change roles, click on View as Roles in the same ribbon.
6. This will filter data as required.
7. Now assign these roles to users to maintain security.
8. Publish the report and go to Power BI Service
9. Go to the datasets. Click on ... and select security.
10. Now select Role created and enter the mail id of users for that role. Add users to roles.
11. Click save and you are ready to go.
This will allow you to now view reports accordingly to the role.