You don't really need to edit the srcds_run file. You run it from the command line and add your server options there. (Any tutorials or documentation about running a Linux server is probably relevant.)
Just open the Terminal application and enter these two commands to take you the directory with the files and run the server:
Code:
cd ~/Library/Application Support/Steam/SteamApps/dummel
./srcds_run -game cstrike +map de_dust -steam
You should then get output similiar to the image below:
