Its necessary to do literally nothing but focus on preparing yourself to sleep in the last 1.5 hours of the day and saying that twice doesn’t make any sense either so lets deep diver with experience.
Lets take an example that what could be the other way.., consider you want yourself to wake at 6am and thus you’ll sleep @10pm and its ALL GOOD. And it sound pretty simple, but the problem is that you cannot go to bed @10pm and expect your body to just switch off. The reson is your body needs a relaxed state of mind to sleep and a target to complete tomorrow morning. So to not disturb the sleep cycle and have the deeper sleep time you need you to do nothing for a time (around 1.hr/1.5hr) but focus on waking up the next morning with a confident mood and mindset.