Each colour is one complete pack of transparent PNG stickers for Goodnotes, Noteful, Notability and any app that takes images. Download the colour you love, or all nine and mix them.
Tap Download under any pack. On iPad it lands in the Files app, in Downloads.
Tap the .zip file once and a folder appears next to it. Open 00_START_HERE_Sticker_guide first, and 00_All_stickers to see every sticker with its name.
In Goodnotes, insert a PNG with the Image tool and save favourites as Elements. In other apps, use Insert image.