Measure the width and length of the interior of the shelves or drawers with a measuring tape. Write these figures down on a piece of paper. If cutting straight is not your strong suit, consider making templates out of cardboard. Simply cut a piece of cardboard to your measurements and then lay this under your shelf paper as a guide.
Use a pair of scissors to cut the shelf paper to your measurements. Remember, it is better to have the paper too wide or long than too narrow or short. Leave yourself a little extra on all sides — you can trim it off later.
Place the shelf paper on the shelf. Some shelf paper has an adhesive backing. Peel off one end of the backing, tamp down one side and slowly remove the rest of the backing, smoothing the paper out as you go. If you do not have self-adhesive paper, you can either glue it in place (which can leave stains) or simply use small, flat thumbtacks on every corner to keep the paper from slipping.
Install real cedar paneling if your armoire is very old (and potentially smelly) or if you simply prefer the smell of a cedar-lined chest. Follow the instructions for lining the armoire with shelf paper, but use a circular saw to cut the cedar paneling to fit. Nail or glue the paneling to each shelf.
Finish off the interior of the doors. Armoires have the added feature of doors, and you can continue your theme from the shelves onto the interior of the doors. Simply line the doors with the same paper or paneling and affix it with glue or tacks.