First, install FORTprint for Mac OSx as described here.

Then, following these steps to set up your Mac for thermal printing:

1. You will be able to access the CUPS printer setting page by visiting the following link: http://localhost:631/printers/. You may also copy and paste it into Safari.
2. In some instances, you may encounter the following error:
   
3. To enable CUPS Control, select and copy 'cupsctl WebInterface=yes'.
   
4. Next, click the magnifying glass in the top right-hand corner of your screen and search for Terminal.
   
5. Once in the terminal, paste in cupsctl WebInterface=yes, and press enter.
   
6. You should now be able to go to http://localhost:631/printers/ and see your installed printers.
   
7. Click on your Zebra printer. You should see a page similar to the one below.
   
8. Click the Administration dropdown, and selected “Modify Printer”
   
9. Click “Continue” on several pages until you reach this final page:
   
10. Click “Select Another Make/Manufacturer”, then set “Make” field as “RAW”. Click “Continue”
    
11. In the “Model” field, select “Raw Queue (en)”, then click “Modify Printer”
    
12. Print a FORT Label