I'm having way too much trouble getting remote tunneling to work. Mainly, just what I need to type into the terminal to get it to work. I understand this is probably a duplicate, but at least that will get me pointed in the right direction.

Here is what I did so far:

1) I went into my Xfinity gateway page and turned on port forwarding.
2) I added both the IPv4 and IPv6 address of my server into the port forwarding setup dialog, along with port 22 for my listening port, whatever that means.
Here is where I am stuck:

What do I write in my terminal to access my server!

Do I write

"ssh username@Router_IP_Address" or "ssh -R (some random thing about port 

22):localhost:(port 22 again for some reason) username@server_ip"

I have been looking for an answer for way too long, and I just need an answer. I have spent 4 years on Ubuntu, and never any problems. This one has been going on for 3 days. Please help me.