This error message means your operating system does not have the proper permissions to the folder where the photo is supposed to be copied into.
So, determine what folder Lightroom is trying to copy the files into, then go into your oeprating system and change the permissions on that EXACT folder to WRITE permission.
now I have 2 questions:
- how can I determine what folder is selected
- how can I chance the operating system for that EXACT folder to write permission?
Sorry for all this questions!
The selected folder is highlighted in Lightroom in the destination panel (scroll down if necessary until you see a folder that is highlighted)
Since you have a Mac, I don't know how to change permissions on that folder, but Google will find instructions for you ... type in "Change Permissions Mac" without the quotes