Try to get your aiming point in the correct part of the screen - your instructor should show you where that is as it will obviously differ depending on if it's high/low wing, and even then an approach in a thruster looks very different to a C42.
The best way to judge the aiming point is to think to yourself "if I did nothing, where would the aircraft crash" and that is where you are going to land. If that point is before the runway, you're too low, if it's halfway down the runway you're too high.
It's easy to overthink these things, best to just get the feel for it and let it come naturally, but one way of breaking it down in your mind is "point and power". Using this method you control your descent profile using your pitch attitude, so you literally just point at where you aim to land, and then use the power to control the airspeed.