Navigate to Dashboard > Products > Categories > enter the category and upload your icon.
If you add a SVG and it does not work you need to open your SVG icons file with some editor like Sublime Text or default system text editor and add width=”31″ height=”40″ attributes to your <svg> tag like it is shown: http://prntscr.com/m4n0qw
Then you will need to re-upload your icons in WordPress Dashboard.