Just make sure you put something comfy/soft under your knees to act as padding. You will work and tonify your chest and triceps.
All these exercises force your body to burn stored energy via your muscles and at the same time tonify those muscles. One thing I laugh about is people believing this will make them bulky. Worry not, at the most what is going to happen is some visible tonification after the first week. Takes years and working with insane weights and number of reps to get to build any significant amount of muscles. What you will obtain, though, with the proper diet, is to burn the layer of fat between skin and muscle. That is what will make you look amazing and feel much healthier.
To me by far the most complicated thing was getting my diet in check.
The are plenty of specialized web services that offer just that but I found these guys to be the best: