It is so easy as uploading the products that use to be part of the shopping list (+ button) and once created it, mark those that you will need to buy (click on the left check-box).
Each product can be detailed (+ button) as much as you want: product name, brand, quantity, price,list and category that belongs to.
A quick search using the magnifying-glass button, lets you find quickly a product along the list. You only have to write some letters.
All the products will be grouped into categories and if you need to do changes, go into the description of each one and edit its details, tapping on the right arrow
After the purchase, if you want to unmark the items you bought to create a new shopping list, it is so magical as shaking your device for unmarking them.