how can I put in a ceiling light in a walk-in pantry with a light switch on the wall. Please make it simple and easy to understand. Include diagrams if possible.

Thankyou for your time.
marilyn_monroe

 

I am assuming there is nothing there currently, one of the possible reasons is the dimensions of the pantry.
The NEC has very specif rules about lighting in closets.
Simply put, if you really want to get it done, get a flourescent fixture (not incadescent, or inca. with CFL adapters) of appropiate size.
Will this be a surface mounted fixture?
To feed this new installation, you need to run cable from somewhere, if this is a kit/dining, it may NOT be from the receptacles. Pick a switch with two cables coming in, such as the ding room, where whites are connected and blacks are on the switch. You must determine which existing cable is the feed.
A volt meter is good here, otherwise trial/error will prevail.
Put pigtail on the existing switch, and connect the pigtail, previosly connected black, and the black from the new cable together. The three whites go together.
At the new switch (pantry), connect the two whites together, and the switch gets the blacks. Be sure to connect all grounds, and ground the switches, boxes, and fixture. Use the same size wire as the circuit you are adding onto is. 12/2 is a fail-safe (large enough either way) Use an old-work box for the switch, a plastic box will be the least fuss with fastening. A metal box typically requires using madison straps. Depending on the light fixture is wheather it need a box behind it. (a Flourescent strip fixture for example doesn't, but optional)

Maybe John can add something I missed, and cite code. (I'm tired)
gj

 

I recommend that you get a home wiring book with lots of pictures. These kinds of projects are well covered in many such books. Much better than we could cover it here.

A number of such books are readily available at public libraries and home centers. Post back here with any questions that arise along the way.