Open the source SDK and Create anew mod.
You can choose between the first three options
- modify HL2 Single player
- modify HL2 Multiplayer
- Multiplayer mod from template
1. The first path is the place where the mod Source file will be stored
this directory contains
This path can be what you want ( ex : c:/mymod/ ).
Note : This directory must not have a gameinfo.txt at his root.
2. the second string field to fill is the Name of your Mod project, as a directory in steamapps/sourceMods/ will be created with the name you choose.
note : prevent to add space and exotic characters.
This is the directory of the final mod, the one you will launch from steam to run your Mod.
And it contains :