Apply the glue: Unscrew the glue tube, invert the cap and press it onto the tube to puncture and open the glue (the cap has a spike in its end). Squeeze a blob of glue onto the hole and spread it with the end of the tube to cover the sanded area (photo). Be sure to make a glue spot slightly larger diameter than your patch. Now wait at least 5 minutes for the glue to dry fully (it'll look cloudy when dry).

Tip: It may seem counterintuitive, but the glue must be dry before applying the patch. You can wait as long as you want -- even weeks. As long as the dried glue remains clean and free of dust and dirt, the patch will stick to the tube perfectly when you get around to applying it.