Problem| My friend cant see my server

I started a Garry’s mod 10 dedicated server and its working alright.
people can log in and play without problems but my friend cant see the server on the list on steam or on garrys mod. when he tries to connect with the IP he gets no responding server and it gives 4 retries and fails :frowning:
How can I fix it?

You have to forward your ports.