If you google “relationship between exercise and sleep” you’ll find a lot of research has been done in this area. So, the first thing you’d want to do is find a unique aspect that hasn’t been studied yet.
Have you ever designed a study or taken statistics? In order to do a meaningful study, you’ll need to come up with a testable hypothesis with little variation between your control group and your test group except the exercise intervention. And before you start, it’s wise to do some estimations to determine how many subjects you need, and how big enough of a difference your experiment will make in others’ sleep habits, in order to reach a statistically significant conclusion.