Here's how to recover a chair step by step. This is the quick and easy way, covering the old cushiona nd material and all. If you really want to do this perfectly, I highly recommend stripping the old material off and the old cushion off before recovering. You want all fresh materials.
fabric tape (duct tape would work fine)
Step one: Remove the chair pads from the frame of the chairs.
Step two: Cut fabric to the size of the pad, leaving ample working material to go over sides. You better off to have too much fabric rather than not enough.
Step three: Starting with the front of the chair fold over fabric. Make sure you line up the design so the cushion doesnt look crooked when it is completed. If this is your first time, I recommend a solid color or print that doesn't have any lines. Staple the front going from one end to the other, do not staple to the corner. Leave about an inch and half.
Step five: Staple the sides all the way to the backa nd leave the one and half inch space for the corners there as well. As you staple the sides, make sure you pull the fabric taut so it is does not have gaps and puckers.
Step six: Finally the back. turn the seat over to assess the look. If you see any gaps you can pull the fabric in the back to work it out. Make sure when you are completing the back that you are stretching the material so that the finished project is tightly on the chair pad.
Step seven: Trim any excess material off and if you want a more finished product tape down the edges of the material onto the chair pad. Place back on the chair frames and screw into place.