There is a handy command to generate the SSHFP records. Type in
ssh-keygen -r <your-domain-name> and the magic of ssh-keygen command will print the necessary DNS records that you have to put into your DNS server.
If you have multiple key types, and want to limit SSHFP records to a certain set of keys, you can do so with the -f option. For example,
ssh-keygen -r <your-domain-name> -f /etc/ssh/ssh_host_ecdsa_key.pub will print the SSHFP records for the public key
The output would look like this:
example.com IN SSHFP 4 1 1b69784a17572ee7e850107f6b3052699a953ad3 example.com IN SSHFP 4 2 b11000d176792edf9c7645aebb2ccdd4a6eb0cf856cadcb6b82ee18e333bef13
example.com IN is part of the BIND and BIND-like DNS record syntax. If you are using any other DNS provider, the part after
SSHFP is what you should copy-pasta. The record type is pretty basic. It's [Algorithm] [Fingerprint type] [Hex fingerprint].