You can have multiples Spaces associated to a single SpaceRunner Project. For example, a building with three floors could have three Spaces: Floor One, Floor Two and Floor Three. You can access the Spaces Gallery from the Spaces link on the Main Menu to your left.
Click on Spaces from the Main Menu
Select the desired Space from the Gallery
In addition if you would like to quickly change from one Space to another, simply select it from the drop-down menu located in the top left corner of the screen