Right click on the folder that says Layout on the bar on the right hand side. Select New Layout, or something like that (don't have it open at the moment)
You would make an event to move your player form one layout to another.
Player(sprite object), on collision with Door(another sprite object) > switch to layout 2 http://www.scirra.com/tutorials/37/beginners-guide-to-construct-2
This tutorial is how I started, and how most of us started. You should definitely check out more tutorials, read the forums, and use the manual if you have a problem. Then if you're really stuck make a post, we're super friendly here and we'll help you any way we can :)