blender 4.2+

Once you download the addon zip file from the store where you purchased it

1. go to EDIT>PREFERENCES, then select the Add-ons tab, click in the right top corner arrow and then click “Install from disk”

2. Navigate to the addon zip file, select it and click the “Install from disk” button

The addon is now installed and ready to use. It will be added as “Procedural Mapping” in a tab named “Sanctus” in the shader nodes editor N panel.
In the shader editor, toggle the N panel visibility with the N key of your keyboard.