How to get a custom IP for a Minecraft server?

I've got a custom domain for my Minecraft server and I've set everything up on www.noip.com but when my friends try and join, it won't let them. What do I do?

Ash

I don't understand, you want to host Minecraft server on you'r PC?
Then you must buy a Static IP, you can request it from you'r internet service provider!

Stojan