Download all files in your desired directory and unzip them all. All blend files are indexed in asset browser and all textures have relative paths so they are ready to drag and drop into your scene. Just download all zip files into your assets directory and unzip.

There should be 6 sub-directories:

flat
grooves_1
grooves_2
grooves_3
grooves_4
grooves_5

and 7 files:

blender_assets.cats.txt

flat.blend
grooves_1.blend
grooves_2.blend
grooves_3.blend
grooves_4.blend
grooves_5.blend

You can of course copy and use files as you please.