Port closed?

Hey guys, so I've been using slsk for years and never had any issues downloading. BUT I can't access some users files, and also, nobody downloads from me. I checked my port and it says it's closed.

The problem is, I am not tech savvy and I have no idea what this means or how to fix it. I know there are many posts here on reddit that explain stuff about routers but I have zero clue what they mean.

Can someone help me configure my settings and open or forward the port, whichever one it is I have to do?