Set up the same way you would for a standard DB bench.
Focus on pinching your shoulder blades (scapulas) together as you lie back on the bench.
This creates a stable shoulder position to press from.
Lay back on a flat bench and raise the dumbbells above your chest.
Twist the dumbbells around so that your palms are facing you (supinated) for the starting stance.
Using a slow, controlled movement, lower the dumbbells until the handles are just above chest level. Feel your chest and triceps loading for the press up.
Pause, then raise the weight back up to the beginning position.
*Tips*
This is an accessory movement so aim for reps and quality technique versus breaking PR's.
Performing this exercise poorly consistently over time can wreak havoc on your elbows.