Hello Kurai,
You see the Corona Renderer does not come with preset materials apart from default one. On the other hand
http://coronamaterials.com is library of materials people produced and published, that is not perfectly organized yet. Sometimes members posting their materials saved in different 3DMAX versions. Few times it happens maps were missing from material. No standard or strict rules being developed yet. Lets hope it will change soon.
Answering your question I create my own routine for importing materials from this site. Usually I do open downloaded file, making sure all paths are correct, no missing maps etc. Cleaning scene from objects i do not need like camera or plane set, consolidating material editor so only slots with materials I do really need left in there (I have to keep it very organized due the farm and network paths).
After that I either save scene with material for the future in my library, so I can easy merge it into my master model when I need it, or creating a new *.mat file and saving material presets in here. And this is basically it.
Do not hesitate to ask any questions, and sorry if we started from the wrong foot.
Good Luck!