Set the seat height so that your arms are upper arms are just below parallel with the floor. There are various ways you can hold the bars, and all work slightly different muscles. There are no right or wrong grips.
Pushing both your back and head into the seat, remind your brain this is a chest exercise and squeeze hard bring your hands too the center.
At the middle squeeze hard and really try and connect with your chest, after a moment or too, slowly and deliberately realise the arms back to the original position.
Once you have started the rep, try and keep the lower arms upright at all times.