Push to a remote repository via SSH


I have a problem to do a mirror my repository with other giltab server. I can´t use letsencrypt certificate because I use nat port and I can I have port 80 open because other server use it so my gitlab is available with port 8443.

So I try to do the same thing but with SSH but when I put a SSH URL and save it doesn´t appear field of password or ssh key.

My version of gitlab is 11.2.3-ce.0 on ubuntu server 16.04.05.

Can you help me please?

Thanks in advance.