Hi Will,
As you are with Workshop Edition, you will have the feature of "Populate Unlicensed File" under "Calibration Tools" which allows you to view the file without licensing the file, as long as it's not tunerlocked by someone else.
So you just need to open the file, go to "Calibration Tools" then "Populate Unlicensed File".
We have a licensing guide on the first page of the CustomOS Wizard.
If the Editor is asking you for 5 credits, its most likely a Standard Custom OS file.
Best regards,
Zhuojian