Firstly, ensure you just download from what we provide you to avoid any confusion or issues. You are correct, create a folder in your Arma 3 Directory called "@Cup_Terrains", all the folders given in the zipped CUP download can be dragged or pasted into the @ folder you created. For the Arma 3 Launcher, you can import all the mod folders from your Arma 3 directory; select "Local mod" then locate your Arma 3 folder and select the folders you would like in the Launcher.
Ensure your mod order in your launcher looks as such:
@506th
@ACE
@CBA
@TFAR
@RHS:AFRF
@RHS:USAF
@RHS:GREF
@CUPTERRAINS
@ALRAYAK
Hope it helps, if you need any other support feel free to find and message me on the Teamspeak server.
Regards,
CPL Leeds