For where to change the category, the site says:
At first, the choice category will be set to gas purchases. As you plan for future purchases, you can update your choice category selection in our Mobile Banking app or in
Online Banking.You can update your selection once each calendar month. If you don't make a change, the choice category will remain the same.
I've already changed it, and don't know if I can fully replicate it, but on a desktop browser, when logging in, select the card, then Rewards, you get the six options, and click the one you want.
For a while, I've only used the card for some automatically set up charges to charity, and when I made the selection today, I thought it said those were all in the Online Shopping category, but I don't find it saying that as I check it again.