FreeDNS - update hash

In the account detail for FreeDNS in the Nextcloud activation page there a “update hash” box. How do I generate a hash for this in FreeDNS?
I have setup up an account in FreeDNS site and added sub domain.

Have you tried the wonderful search function of this forum:

The process is also described here:

https://pant.github.io/nextcloudpi-test-docs/en_How-to-access-from-outside-of-your-network.html