(1) Verify that MOPAC has already been installed and is working.
(2) Download the MOPAC App, and put it in the /Applications folder on the Mac.
(3) Double-click on /Applications/MOPAC.
The application will not open because it was not
downloaded from the Apple store.
Instead, there will be an error indicating that
security will not allow it to be opened.
If there is the option "Open", click on that.
Otherwise, go to System Preferences => Security &
Privacy => click on "Open anyway" for MOPAC
(4) "Drag and drop" the MOPAC icon from the applications folder to the
desktop.
This will produce an icon that has a small arrow
on the desktop.
(5) Open a folder that contains a simple MOPAC data-set.
"Drag and drop" the data-set onto the MOPAC icon on the
desktop.
An output file should appear in the folder,
indicating that the job is running.
WARNING! Simply clicking on the MOPAC icon will not work. The icon works by "dragging-and-dropping" a MOPAC data-set from a folder onto the icon. Also, look for the files generated by MOPAC in the folder that contains the data-set.
MOPAC can also be opened using the Mac "Open with" option.