SSH Tunnel through Android device
if you are in the same network as your friend, you may just connect
if you are in a different network and you want to connect to the computer through your android phone, you probably have to forward the port from your mobile Internet access to the machine, I think this is not possible
you have to use a vpn to your private network and put those two virtual networks together (your vpn and your LAN) then you might connect your friends pc to that vpn and access it as it would be in the same network as you. recommended but maybe not easy because you have to set up a vpn server on your local machine and make your friend connect. 
if you have to use the android access point, you will have to connect the android to that vpn and route your friends traffic through the vpn, not easy and also requires changes on your friends machine