Use the green flag to start the scripts. The left and right arrows will move the walking girl sprite towards the doors. The sprite will move from backdrop to backdrop depending on which door she walks through.
This is based on something I saw a long time ago on Youtube so I can't credit the creator. This is an example of how a sprite can move or walk from one scene or backdrop to an other. In this case, the sprite can walk around in circles from room to room through all four backdrops.