To use these greebles in blender 2.8 and above is quite simple:

1. You can open the blend file with these greebles alongside your already opened blend scene and then just simply copy/paste whichever greeble you wish from one Blender window to the other.

2. While inside your scene, you can go to "File -> Append", browse to where you saved this greeble blend file, click it and go to "Object" folder and finally append any/all greebles you wish to your current scene.

Please check the FAQ section for more info.