Dear Frances,

From your postings and the replies you got from me and others has not helped you much - or so it looks from your fresh questions.

Fortunately the topic of power supplies is a very well documented one and and all that is required is for you to walk ( or drive ) to the nearest book shop and pick a book that teaches the basics and shows some practical circuits.

And if that is difficult look for tutorials on the net on linear power supplies.

Good luck

Raghu