Simple answer: you don’t. A well fitting bra will not ride up. Your bra, once clipped up, with your bust adjusted into it, should not move all day.
However, many ladies feel the need to keep pulling the bra down their abdomen, towards the waist. That riding up feeling is because the band has too much give. And every time it is pulled down, it is stretched that little bit more…
To give your bust proper support, to prevent back ache, and to enhance your posture and profile, the bra band must be a firm-ish fit. With a loose band, the straps and cups cannot apply the resistance needed to hold the breast up and away from the body.
Next time you take off your bra, look for the line where your bra was sitting. It should be a faint indentation, or noticeable line. Not a pressure mark, just an indicator. That line should be right under the bust, not an inch or two below. And definitely no where near your waist.
If you can’t see that line, it probably means your bra is too loose, doing very little in the way of lift and support. In addition there can be friction, and potential skin aggravation from the constant sliding and rubbing.