How do i add in bastion server into the ssh gateway when i don’t know its password?

How do i add in bastion server into the ssh gateway when I don’t know its password but has root access using my ssh keys?

  When you add in the target server into the ssh gateway, choose the password management as ’keep server password’ and manually add the ssh gateway way public key which can be found in Servers->Global key into /root/authorized_keys file on the target server