AngelEyez, you ARE contributing. You are posting messages and asking questions. The vast majority of people visiting the site on a regular basis don't say a word. So don't feel bad. Download all you want - that's why skinners post their skins, for people to use. They don't expect anything from you in return (well, maybe a few words of encouragement on the comments page).
As for making skins, I've been with wincustomize since the start, and only now am I contibuting skins. Like you I didn't understand the program, I also couldn't design anything. Some of my skins are now almost worthy, most are useless. It take time to learn even the basics, but have a go, it's fun. If you end up finding skinning isn't for you, that's ok too; as long as you are getting pleasure from the skins you download, that's what its all about. Oh, and keep asking those questions...