How to install expansions:

• Download the REAL2PIX-fabrics-shaderpack-01.zip file from the store where you purchased it.
• Extract the content in a local folder of your choice
• Open Blender and go to Edit > Preferences > File Paths
• In the Asset Libraries press the plus (+) button and add a desired name and the file path to the folder where you extracted the files in the hamburger menu icon save preferences
• Now you should be able to access the assets from the Asset Browser