pete_elms,
The easiest way would be to re-use a management role that already exists on the ClearPass Policy Manager side. On the ClearPass Policy Manager Side, go to Administration> Users and Privileges. Click on Admin users and Create a user with privilege level of Help Desk. Remember the username and password.
Next, go to the ClearPass Guest Side by going to Dashboard> ClearPass Guest.
Go to Administrator> Operator Logins> Profiles and Edit the Help Desk operator profile. To manage Web Content, you would need to modify the Help Hesk operator profile so that it only has Custom Access to Platform and Full access to Content Manager, which allows uploads and deletions of HTML content. Make sure other options like Guest and Onboard also have "No Access" next to them.
web-editor.
Open a different browser and go to https:<ip address of clearpass>/guest/auth_login.php and login with that helpdesk user you just created. You should be able to see and upload content. Depending on what you ultimately want to do and the type of testing, you probably have to enable more permissions in the Help Desk operator profile.