Assets from the ‘3D Viewport’ catalog (Backdrop, Disco Ball, HDRI World) can be dropped directly in the 3D Viewport.
Assets from the ‘Compositor’ catalog (Streaks, Sun Beams) are nodes that can be dropped in the Compositor.
NOTE If you can’t see any assets, make sure that all Filters are checked (turned on) in the top-right corner of the Asset Browser window and that the Search bar is empty.
If you are using the Asset Browser for the first time, please **SEE THIS VIDEO.** It has a lot of great info that makes it much easier to understand and use the Asset Browser.
No downloaded files need to be opened. Simply place them in the right location.
Some useful info about ‘Import Method’ in Asset Browser