Help with installing DarkRp

This version

I am trying to extract darkrp to my addons but when I do it doesn’t show up as a addon option, only sandbox and trouble in terrorist town, can someone give me a detailed tutorial on how to install it for gmod 13?

[editline]4th December 2012[/editline]

I fixed it, when I downloaded it I didn’t know you were suppose to remove -master from the file name, hope this helps anyone with the same problem.