How to open ssh access to the server from outside (from any ip)?

Question

SSH

There is a server on ubuntu, it has two network interfaces, a twisted pair cable is connected to etho from the main network with the Internet. From eth1 comes a new subnet 192.168.20.0/24 (as an example). I connected a PC on Windows to a new subnet, received the address 192.168.20.4 via dhcp. From Windows I connect to ubuntu (openssh) via putty to the address 192.168.20.1 port 3124, everything works.
Now I want to connect to ubuntu from another PC, from the outside (from another network), how to do it???

Answer 1

forward the port on the router. if the second network 192.168.20.* has a connection with the tyrnet through a router.
option 2: describe where the "twisted pair" with "eth0" is connected. because neither the system for connecting to the Internet, nor the address, nor any other technical parameter is described here ...