From Shoot Em Up Kit
To set a background sprite for a level, click the Edit Background Settings button in the Level Settings window to open the Background Settings window and then click Sprite Background to open the window section.
Click on the Sprite box to select a sprite.
Click on the to remove the sprite.
Click on Scale and Rotation to open the window section to set a scale and rotation for the sprite.
For a moving sprite background, select the scroll or rotation direction from the Movement drop-down list and set the Speed. Check the Wrap box if the scrolling sprite is to keep repeating.
It is possible to have several layers of background sprites. To add a new layer, click the Add New Layer button. Use the Depth slider on each layer to set the position of the layers, closest to furthest.