The thing about "Secret URL" is dated, you do not actually validate it on the HWbot site.
Instead you do it here: CPU-Z VALIDATOR
Be sure to bookmark the link.
Also make sure you are trying to validate a result with the most recent version of CPU-Z, as revisions are released results from older versions will no longer validate by design.
As to how:
Best way is after you visit the above link, look towards the bottom center of the page and you'll see the "Manual Validation Form", that's what you'll use.
1: Enter your benching name on the "Name" line, the next one about an email is optional.
2: Where it says "Select your file" just click on that and manuver to the folder/place where the validation file you want validated is and select it. Just make sure you have it in a place you can find it easily before you click the link.
3: Click "Validate".
4: For your submission entry, make sure to actually bookmark the page that appears with your result - You'll need that link for the submission.
Hope this helps.