Currently, we don't have documentation for the module. It is, however, a scheduled task for our team.
To address your specific question:
1. Install the module in the normal way
2. Click "Edit IFrame Settings" link (or select this option from module dropdown menu)
3. Specify the full url to the page you want to have inside the IFRAME.
4. If you want to pass parameters to that page, click "Add Querystring Parameter" link - it will show a line of controls - type a parameter name as you want it to be (in your case it would be userID) into a textbox and select the relevant value from the dropdown (in your case it would be User Id)
Update the settings is you are ready to go. Of course, width, height, etc. should be set as you'd like.