I am using Blender 2.8 and cycles render I wanted to download a few materials from websites like http://matrep.parastudios.de/ when I download the files I follow what others have said to do. select file-append and then select the blender file and select the materials in the material folder in that blender file. when I do this I select the blender files but then there is nothing there is no other folders..what I am doing wrong, is there a plugin for 2.8 that helps with stuff like this there is the material library addon you can load by default.
The downloaded files from that old site do not appear to be blend files, which is why appending does not work.
While there have been a few different material library addons, there are two options that are currently working (and included) with 2.80. The first addon is listed as Material Library and was previously called "matlib vx", the other is a new addon called BlenderKit which provides a much wider library of resources that includes models, scenes and brushes.