First get yourself in a push-up posture. Ensure that you align your body with your head and your hands are under your shoulders. Also you should apply pressure to your toes in this posture. You should then bend your elbows towards to floor and backwards to a 90 degree angle.
Ensure that your body is straight always. Your arms will be extended completely only when you are pressed back. If you are not able to do regular pushups, you can try the knee pushups.
Position your hands shoulder-width apart on a secured bench or stable chair. Slide your butt off the front of the bench with your legs extended out in front of you. Straighten your arms, keeping a little bend in your elbows to keep tension on your triceps and off your elbow joints.
Slowly bend your elbows to lower your body toward the floor until your elbows are at about a 90-degree angle. Be sure to keep your back close to the bench. Once you reach the bottom of the movement, press down into the bench to straighten your elbows, returning to the starting position.
This completes one rep. Keep your shoulders down as you lower and raise your body. You can bend your legs to modify this exercise, if it’s too hard!