Hello @PR,
You must copy and use the full name in the code, such as (et-icon et-shopping-bag). This should work for you. Please refer to the screenshots provided here: https://postimg.cc/47rTGXFW and https://postimg.cc/1VPJwTg9.
And you can use the FontAwesome Icon from Google: https://fontawesome.com/
Please refer to this thread as well: https://www.8theme.com/topic/fontawesome-xstore-icons-will-not-show-in-menu/
Best regards,
8Theme’s Team