Organisations prove control of their website's domain in one of two ways.
A DNS record
Add a TXT record to your domain with this value, using the token shown in the developer console.
krodium-verification=<token>
A file on your site
Serve the verification file shown in the developer console from your own website, then ask for the check to run again.
DNS changes can take a while to spread. If the check fails at first, wait and try again.
Still stuck? Write to [email protected].