I have both the mod and the game installed but whenevr i load up the game it just goes into the original game not the anomaly mod. is there somewhere i have to select it or something. i though the one click mods just play automatically. please can someone help me im almost ripping my hair out!

Anomaly is a standalone mod. Since it changes the binaries, you should not install it to your CoP folder. There may be a misunderstanding between the Anomaly folks and GOG.

I was surprised to hear it was available as a mod from GOG. The permissions given by GSC were relatively strict, I thought -- they allowed the existence of the mod but did not allow any profit to be made from it. The binaries were built from leaked source code.

the original game is based on the 32bit X-Ray engine,anomaly is based on the (newer)Monolith 64bit X-Ray engine.
Means,you MUST install anomaly in a seperate folder.
if you can`t get it to run,you could check out www.moddb.com/mods/ stalker-anomaly.Everything is there,anomaly download,addons,etc.