Thanks for including the exact error message; that helps to diagnose the problem. You're almost there.
There is a space missing in the command you tried. You have to type chmod +x /Users/... with a space between "chmod" and "+x" in addition to the space between "+x" and "/Users/...".
My error message was: "No such file or directory" , and the unarchiver tells me "The contents of "Ashorthike.app" cannot be extracted with The Unarchiver, what should my next step be?