Step 1: Take off the seat.
Step 2: Choose your fabric. (I chose to cover it in white first, only because I was afraid my fun fabric was too thin…and the green might show through. Normally you probably wouldn’t need to do this…)
Step 3: Cut enough fabric to allow roughly 2.5 to 3 inches on each side.
Step 4: Firmly staple the middle on each side.
Step 5: Work your way around tugging lightly and stapling the fabric in place.
Then happily screwed it back on my chair.