Mrs. Smith,
I really, really hope you don't try this yourself. Please find somebody who seems credible, and who feels comfortable doing this himself (or herself), who will be physically present to give you instructions, or do a little show-and-tell.
That way, you will survive to (carefully) fix/replace the next light fixture that breaks. It's not the sort of thing that's terribly complicated or difficult to learn, but it can be dangerous, and you need a little basic instruction.