Eidgeniesser

My internet connection comes from a mobile hotspot. so I dont know how to do the port forwarding part to play 0Ad online. Also I dont know how Port forwarding works in general and what its for. So i have an app on my android which is clled port forwarder. Is it possible to forward the port from there and if yes how do I have to set the settings? Or does the hotspot not work as a router? How would i enable MP then? Would really like to play the game MP, so am thankful for any help.