opening in Xcode

Could someone explain how to open a mac intel only .app from unity in Xcode? i've scoured the internet have done for days and found no useful tutorials, if someone could explain the process to me it would be great! i have no xcode knowledge at all! i am doing this because i understand it's the best way to code sign and package for the mac app store, selecting 'open other' in xcode opens it but it doesn't give me any usable options this way... thanks in advance