I think you mean that you want to connect to the home server from outside your home, correct? You don't really connect via SSH to the router for this; you just tell the router to pass the connection on to the home server. If this is the case, read on. If not, clarify the question even more.
You will have to tell the router to pass incoming traffic on the SSH port on to your internal server. This is usually called "port forwarding" or similar. See Google or perhaps http://www.portforward.com/ for specific guides for your router on how to accomplish this. It is usually handled via some web interface that you see when you enter the routers internal IP address (usually 192.168.0.1 or 192.168.1.1) in a browser from within the home network.
Forward e.g. port 22 for the TCP protocol (the standard SSH port) from your router to your home server. After this is done, and you have an SSH server running on your server, you can just connect via SSH to your external IP (which is "owned" by the router), which will forward the connection to the server.