You need more than that, you need to configure destination address translation or port forwarding
For example
Your router public IP is : A.B.C.D Your router private IP is : 192.168.1.1 Your ssh server IP is : 192.168.1.2
Then you need to setup DNAT so any packet arrived A.B.C.D:22 will have destination IP translated to 192.168.1.2 and forwared to your SSH server.
Do some search on port forwarding, it is easy to setup.