Open up the fitted bottom sheet and spread it out over the bed, with each sheet corner on top of a mattress corner.
Connect one clip of a mattress suspender to one edge of a sheet corner. Stretch the suspender down under the mattress and back up again, crossing under the corner. Connect the other clip to the other edge of the sheet corner. This will hold this corner of the sheet in place.
Repeat the process with the opposite diagonal corner. Do the remaining corners to fully secure the fitted bottom sheet.
Lay the top sheet on the bed with the side edges even and the top of the sheet at the head of the mattress. Tuck the bottom of the sheet into the foot of the bed with a hospital corner. The sheet will cover the larger mattress, but it won't have much overhang on each side.
Cover the top sheet with a blanket. Tuck the bottom of the blanket under the foot of the bed. Cover the entire bed with a bedspread or duvet.