There are a number of books available on precision and non precision approaches. Take a tour around the Transair site on similiar.
One of these would give the theory. To be able to do it you need to do the course (basically IR) to be safe and effective.
Best to get an appreciation of the concept with an instructor on your PPL (as above) then concentrate on the basic VFR flying for now, so you can do this (running & walking etc)
Gd luck,
h-r