It would work like any other 3rd party website verification, e.g. some of these options that Google uses for their webmaster tools:

https://support.google.com/webmasters/answer/9008080?hl=en#c...

Uploading a file that contains a token and then serving that file at a specified URL is common.

So, you'd need to go and claim the money that yep.com is apparently going to keep track of for each site or subdomain.