We are just integrated UPS with NS and we are trying to integrate our thermal printer via a USB port to print when hitting the save and print label option on the item fulfillment. When clicking save and print label it just downloads the label in a ZPL format. How do I set up NS that it should print from the printer when selecting the Save and Print label option?

You have to use the zpl file provided to print the label. You can set your browser to automatically open the files and send them to the printer using the NetSuite instructions. Share the printer and create a batch file. Search "Printing Integrated Shipping Labels with a Thermal Printer" in help center.

noted, thank you!