Which feature do you mean exactly? Also what do you mean with your second question? Can you elaborate? You can earn money with your shop either through the affiliate commission or either through the design price: https://help.spreadshirt.com/hc/en-us/articles/210769049-Earning-Money-with-Spreadshirt
You can also watch this video: https://www.youtube.com/watch?v=YWPym2AEsW8

Let me know if I can be of any further help.

Thanks,
Lena