Enter this link, read everything and see if it solves your problem.
And yes, if you are running the server on your machine you need to release ports etc, in case no one is able to enter the server yet.
[EDIT]
I saw it now, L2D4... Release your router ports;
I don't think this is what I wanted, I just need people to come into the server, and I also want to know how to apply plugin to the server. I think My server is only for windows.