Project file can't be build error you don't have permission to view it

Hello may be this is silly question and may be asked before it but i am not getting proper solution for this. I have downloaded one project from the internet and when i am trying to run it/build it the xcode says :

The file “PROJECT NAME” couldn’t be opened because you don’t have permission to view it..

Can anybody have idea why this is happen ? Please help me to resolve this issue