The Push-Up is generally more challenging when performed on kettlebells. But it is not a requirement here. The Push-Up is a great exercise for the core and stabilising muscles. A familiar movement would usually be performed with dumbbells and barbells on a bench.
The Push-Up is an excellent upper-body exercise to build strength, muscular endurance and power; perfect for muscle isolation whilst tying in the core and working the chest and arms.
1. If you are using kettlebells for this place two about shoulder width apart on the floor. Making sure they are flat, come into a push-up position with your hands on the handles. The grip should be neutral with your fingers underneath the handle. If you are performing this without kettlebells position your hands on the floor directly underneath your shoulders. (See Fig. 1)
2. Keeping your torso straight lower yourself towards the floor, bending at the elbows and feeling the tension across the chest. Maintain a neutral spine throughout.
3. As you hit the lowest point, steadily and carefully push back up, straightening the arms back out. Repeat the movement from point 2. (See Fig. 2)

Fig. 1

Fig. 2

Throughout the whole movement the body should be tense, with your abdominals drawn in and shoulders positioned back and down.