Downloading/uploading new themes on a Mac

Hi,
I’ve recently moved from a PC to a Mac and am having some difficulty uploading new themes as a package. What happens is when I download a new theme to my local computer, it seems to unzip the files so that when I go to upload a new theme, I can’t grab all the files to put into the themes directory.

Is there something I’m doing wrong or is there another step required on a Mac.

Confused.