Measure, Cut, Glue
On paper, make a rough estimate of the size of the underside of each chair leg (the inch or so that touches the floor). You can use a measuring tape, or just draw pictures of the outlines. The goal is to get an idea of how much space you need to protect in order to purchase enough felt.
Go shopping. Everything you need can be purchased at a craft store or large discount store. Buy a felt square, large or medium, in a neutral color--brown or tan for wooden chairs.
At home, turn over the chairs and, using the marker and the felt, outline the chair edges that must be covered. Make these outlines slightly larger than the edges---they can always be trimmed, but you will have to start over if you make them too small.
Cut out the felt with scissors. Cut out two pieces for each one needed. The pads will be doubled to make sure the floor is protected.
Squeeze a couple drops of glue onto the chair ends. Do not perform this step until the felt squares are ready. Stick the first layers of felt to each chair end. Pour a couple drops of glue onto the first layer and affix the second layer.