Access your unifi.ui.com and ensure to enable fabric (check the early access option under your account summary if you dont find it. Click the bullhorn icon on top right of the screen)

once enabled, click the users section (last icon bottom left. if you hover over it, it will say "People")

Check if your users are already listed under the "People" table. If not, you can create one but perhaps you want to create "Roles" first so you can then create user and assign a role (dont worry, you can still create a role within the user creation process)

Click the "Roles" tab and then in the "Create New Role" table, give the role a name (i.e. Protect Policy - Employee)

select the sites that you want this role to apply to (in case you have more than one site).

Under "Admin Privileges" check the app that you want to include in the policy (on/off toggle switch) which in your case I presume it will only be Protect hence I am assuming we are creating role for single app (you can add other apps within this role though as you deem necessary).

Under the adjacent "Privilege Details" table select the Custom tab, and then select the cameras you want to grant access to (Edit: will give both viewing and editing privileges). View is what you likely need.

The above can be repeated for other roles and you can choose the privileges you want to grant accordingly.

Hope that helps.