When you start descent or climb, you will see a whitish line with slight curve move closer to your aircraft on the line of your fpl. This line will be able to tell the location you will reach that altitude with the Rate of Descent (ROD) and speed you’re currently going. You will be able to adjust your vertical speed rate using that arc of white line in front of your aircraft until it will reach your set altitude.
Another notable step that you can use without formulas is Virtual Hub on your mobile or tablet. There is this section on the app saying TOD (which means Top of Descent), and what you will need to do is enter your Indicated Airspeed which is displayed to the left of your HUD, then your planned altitude and cruising altitude. It has made me successful in my TOD everytime ;)