Can't Connect to My Ssh Server?

I tried for the first time to setup a ssh server following these steps on the server machine:

1. Following this article, I installed sudo apt install openssh-server
2. Following this question, I edited /etc/ssh/sshd_config and appended

   Port 22
   PermitRootLogin no
   AllowUsers usr
   

3. Following the first article, sudo systemctl restart sshd.service
4. Following this article I found my external IP address ip-add using this
5. I tried to ssh from my server machine to the machine itself with ssh usr@ip-add

However I got this error message:

ssh: connect to host ip-add port 22: Connection refused