Gmod internet server help!!!

hi everyone thanks for looking at my question.

right i want to make a server that other people can join. i currently have a server but it a lan server. i made it using hlds updatetool. i have it and it works it comes up in the lan section in gmod. now how do i make it so it appears in the internet section. no one can join my server at the mo. i herd i need to port forward my server but i cant find the option on my router. i have a bt-homehub 2.0 router. i have a setting for application sharing but i cant enter in my server ip and stuff. if someone could give me an explenation on how to make this a internet server i would be very greatful. (im not that experienced with computers so keep it simple. lol)

thankyou

xdemonx456

Port Forwarding, Router Specific