Co-op mod help :)

[Deathx113]

Alright... I tried downloading a mod, well a ton of different ones. Anyhow, I am trying to use the one the one that says "spelunkycooptest8mod", but how do I use it?
I load up the game and it asks if I want to host or to connect.

If I click connect it asks for an IP, what do I enter, or where do I find what to enter? (I am trying to do a lan game, my computers are sitting next to eachother :p)

Also, if I click Host it just says
"Can not listen to port 14804"

Please help, thank you.

EDIT:

Or, if anyone wants to, could you explain how to start up a multi-player game?  Using any mod you like best haha

[Nathan Cash]

Port forward. Also you can only play with people that you know there IP

[KarjamP]

Also, take note that the mod's incomplete.