The notetags are explained in the respective tabs (Item List Window & Item Detail Window (Image). Basically, when your image file has the name "Potion.png" and is located in img/pictures/items, then the notetags are
<Menu Grid Image: items/Potion> <Menu Image: items/Potion>
The second one is used for the item inspection window on the right.
A sample game is not planned for this project as making some and keeping it up to date is a lot of additional work.