Here are the steps I used to make a scrolling scene. The two problems I usually have are forgetting to adjust the floor (step 9), or forgetting to change the resolution of the Main layer (step 5).
(I didn't leave any details out, so it is frighteningly long, but not difficult.)
For this example, my display resolution is 1024x768. My background is 1400x1050, but you can change to suit your needs, as long as the background is bigger than the display.
1. If you need to, create a new project using the Basic Project template.
2. Create a new scene. I chose the "Empty scene -1024x768", but it doesn't really matter. Make sure you copy the scrolling background to the scene folder (in my example case it is a 1400x1050 background.)
3. Open the new scene in the scene editor.
4. In the layer palette, click on the Main layer -- where it tells the size of the screen (usually 800x600) -- to select it.
5. Now click on the "Layer Properties" button just above (with the hand pointing to the page). Change the width and height to match your scrolling background -- in my case 1400x1050 -- and click the OK button.
6. Click on the background entity in the entity palette to select it.
7. Click on the ... button next to the Sprite path in the Entity Properties section and select the scrolling background, then click the Open button.
8. Now reposition the scrolling background where you want it. When you look at the scene, you'll see a red outline around your background, and a blue outline -- that is the floor. If you use the scrollbars you should also see a light gray outline. That is the outline of the display. Now reposition the scrolling background relative to this gray outline. In my case, since the background is taller and wider than the gray outline, I adjusted it so that it corresponded with the display outline on the left and top, and extended beyond the gray outline on the right and bottom. (Note that if you forgot step 5, you won't be able to scroll to see all of your scrolling background.)
9. Finally, click on the Floor entity in the entity palette, and then adjust the floor (positioning the mouse over each corner until you see the + pointer and then dragging the point, and adding and deleting points as needed) so that it the character can walk to all parts of the scrolling background that you want accessible. Keep in mind that if the actor can't walk to an area, the game won't scroll to it.
10. Save the scene and play the game. (You may need to make the new scene the startup scene if you don't have some way to get to it.) The scene should scroll when the actor walks around it.
