For all the possible things to include, see
Template:Citation
Of course, you don't have to put everything in, just whatever you can. The above example is a book, but I've included a 'convenience link' to a website that displays it.
Then, at the end of the document (but before any 'category' tags), you need a references section. You just put,
I hope this makes sense; the best thing is to experiment in your own area (e.g. user:Str 88/test), and also to look at other articles and copy from them (especially featured articles, which should have good refs).
Hope this makes sense, cheers,