blender 4.1 and earlier

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, and then click the “Install” button

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