Well, It isn't very complicated.
The easiest way if you're not good with forwarding ports, Is to download Hamachi for yourself and your friends and create a network, Tutorials are all around YouTube explaining how and it's very simple. Once you create a network, A VPN IP will be assigned to you, It will be displayed on top of your Hamachi window, Right above the username you chose. Make your friends all join your created network.
To create a server, You first need to activate the console in the game's options, Usually located in
Keyboard -> Advanced -> Enable Developer Console
Then when that is done, Use the tilde "~" or "`" key to open the console. This key is usually located to the left of the number 1 and over the TAB key.
If it still does not open, It's most likely because your keyboard language is not in english, The easiest way to open it is to right-click Goldeneye Source in your Steam Library, Click properties, Then launch options, And add "-console" (without quotes) in the line, Then press apply, And re-launch the game, The console should be open, Just make sure you do not close it.
To start a server, Simply click "Create server", Then choose the game's options and map, And click start.
Once you're in the game, Press escape to open the menu, The console should still be there, Enter "sv_lan 0" (Without quotes) and then heartbeat.
When everything of this is done, Tell your friends to go in their server browser, Then go to favorites tab, Tell them to add a server to their favorites by right-clicking on the server list, Then add a server, Then tell them your Hamachi IP plus the default port (Remember, They have to be in your Hamachi network or else they won't see your game!)
So your Hamachi IP should look like this when adding it to their favorites :
xx.xxx.xxx.xxx:27015
Then they should be able to join your game.
I don't know how to make myself any more clear than that, So good luck!