The brushes on this site are very simple brushes created from various images. They are fun for new users to play with, especially when they are just learning about brushes and the concept of using a digital brush.
How to install brushes
Download and unzip the file to a place where you can easily find it. Once the file is unzipped, simply double-click on the .afbrushes file and the brushes will install themselves. It will automatically open Affinity Designer and put the brushes where they belong.
An alternative would be to open AD, click the Brushes tab, then click the menu and select Import Brushes. Navigate to where you unzipped the files and import.