The Pricebook Maintenance function allows you to modify or add items to your Pricebook. Modifications and additions will them be uploaed to My Pricebook and then to your register.
If you want to edit or remove an item, tap on the item you want to change and the line will highlight in blue, then tap Edit item. The app will take you to screen 2 and you can change the information or tap to delete the item.