STEP 1. Within the Finder you have to choose the app or file you want to edit permissions for.
STEP 2. In order to get info about the selected file simply click on Command+i or you can go to File > Get Info.
STEP 3. Now you will be able to see “Sharing & Permissions” at the bottom of the Get Info window, Simply select the arrow to drop down the options.
STEP 4. Now you can adjust permissions per user: read only, read and write, no access.
Now simply close the Get Info window. That’s it. Now immediately the changes will take effect. In this way you can change the file permissions in Mac OS X quickly.