We don't support preview print on Safari & Firefox.
In other words, you won't see any printer icon on the previewer.
On Safari & Firefox, the alternative way is to download PDF and print.
Step-by-Step
Move the mouse to Generate Labels button and click Download on the product/address label page.
Firefox will open the file automatically. Click the Print icon.
3. Click the Print using the system dialog at the bottom as the above image.
4. Set the correct Printer, Paper Size, and Orientation.
5. Set Scale to 100%. ( Orientation can be different on different devices, according to the preview screen to select Orientation. )
6. Click Print.