With the decline push-up it is important that you position your feet higher than your chest. This can be done by placing your feet on a park bench, or on a swing for instance. Place your hands on the ground and slightly wider than your shoulders. Inhale, bend your elbows and lower your body. Exhale, straighten your arms and return to the starting position. The higher you place your feet the greater the challenge. Ultimately you could progress towards a full handstand push.

Decline push-up on a park bench