Difficulty installing Themeforest theme on wordpress on a mac

have bought a theme forest theme and am trying to upload it on wordpress. I get to the point where I am asked to upload the .zip file. When I click the avada.zip file it comes up with an error message – ‘are you sure you want to do this’. If i try to upload any of the avada package files it will only allow me to pick one subfolder at a time. Is there a different way of uploading from a mac than from a pc? I’e tried to follow the demo video on the theme for how to install but my mac doesn’t give me the same options as the person on the video? Any help greatly appreciated!