Adding a band to the dumbbell overhead press places extra resistance at the top to build your delts along with parts of the back musculature.
Grab a light to moderate resistance band and wrap it around your back, preferably the lats. The band won't slide down when you start pressing; it'll wrap nicely around your upper lats and underarms. Some people may use two bands on each side, but it's more effective with one band.
Grab the dumbbells (or kettlebells) with the bands around your thumbs and find the grip that's best for you.
Hoist the dumbbells up with your knees and put them safely on shoulders. Press the dumbbells upward until they touch and lower them to the starting position.