The main panel where the Materials are now has a switch to change from Materials to GN Assets
Like in the Materials module, you change the category and select the asset that you want to use.
There are 2 ways to use the assets:
1. “Apply Asset to Object” Button adds the asset (Geometry Node Modifier) to the selected object
2. “Add Asset” Button adds a new object that contains the asset.
-Most parameters will show in the addon panel when selecting a Geometry Nodes asset. But there are a few others like the assigned materials, target objects or collections that will only show in the modifiers tab.