How to adjust the density and speed in the settings?

For "Munbyn Print" App :

After creating your label, select "Settings" on the "Print Preview" page to adjust the density and speed.

For Windows :

You can do this by entering: 
Settings -> Bluetooth & devices -> Printers & scanners -> Click on 'ST425' ->  Printing preferences -> Page -> Density/Speed->Apply.

For macOS:

(1) Click "Printer..";

(2) Choose "Printer Features";

(3) Adjust the Speed and Density.