First, find the My Files tab in the menu on the left. Here you can find your uploaded images or upload new ones. Note, the file shouldn't be more than 50 MB.
In the Fonts tab, you can upload any fonts you like or find all the fonts you’ve added earlier. If you delete custom fonts, they will be replaced by the standard ones.
All the items you purchase will appear in the Purchase tab. You can use them again for any of your designs.