There are normally two different hand positions on this machine and they both work slightly different muscles. With the palms forward, push your back into the seat, drop your shoulders and push them back and focusing purely on the shoulders lift the weight.
At the top stretch for the ceiling and also engage your triceps. Pause for a moment, really thinking about the two muscle groups you are using then slowly and deliberately lower the weights. Don’t let the stack touch the bottom but begin the next rep without any pause for thought.