How to Connect to an SSH Server That Is Port-Forwarded on Another Network?

I am having trouble (a lot of it) grasping the concept of port forwarding ssh servers. I want to be able to connect to a device on another network that is port forwarded. How can I do this?

Box 1: Separate network

Box 2: Port forwarded on port 4444 external and 22 internal (assuming the router re-directs 4444 to 22)

How exactly do I connect to it?