To Use the Assets :

you need to first create an Asset library folder in edit >preferences >file paths

Then download all the files in that folder ,In there you will find  Catalog.txt  ,   Open it and copy this code:    

Now in the Asset's folder you should find an blender_assets.cats.txt ,just open it and paste ,'remember to leave no spaces'. 

Now you should see all the Assets in your Asset browser      

Also for Collection Asset's just click on the add collection menu 

 and Uncheck Instance:

                                                                                       ENJOY  :D!