When creating a study, you can leave it in a "preview" or "building" state, or you can launch the study if you are ready for it to be live.
(Note that as you build, the study is auto-saved. If you simply walk away from it, you can return to its last known state from auto-save)
There is not a way to schedule a launch for a different time or date in future. When you press "Launch", the study is live!
Please note that after a study is launched, possible changes are limited. For example, you cannot change the starting URL, add or remove questions, or change the type of study that you have created. (from 'my own testers' to 'panel', desktop to mobile, etc)