1.) Add a Reach Marker or Talk to Contact on design surface.
2.) In the lower left of the screen it warns you that you need to place all components before proceeding.
3.) Click on the component and select the next map. Remember to achieve the warp out/in for space and the ground beam in-/out you need to keep the following in mind.
(space: always from space-map-to-space-map)
(ground: always from ground-to-interior or vice versa)
If you try and go from ground map straight to space you will suddenly appear in space, with your ship in front of you. It is always best to go from ground-to-interior like a ship and then to space. That's how it would really happen
You have a limited of 10 maps, so plan out the transitions before you start so you know what you have to work with from the start - create the template for your story, then use a utility like FreeMind a simple, free java app that allows you to break apart the storyline into a tree.
4.) The Transition dialogue will now allow you to create the transition.