This is a tut for those who just want to scroll or fade a series of images.
First thing's first: know what a sprite is and how it works
1. instantiate a sprite.
2. draw a rectangle (or whatever shape you'd like) within the sprite in the area you want your pictures to be seen by the awestruck public. In the sprite's options make sure you check "use bottom object as mask"
explanation: the last object in your sprite is the "bottom object" for obvious reasons. If you have a large object as the "mask" and all your images are smaller than the "mask" AND inside the area of the mask itself then they will be shown, but if your images are larger than the "mask", only the part of the image within the "mask" will be seen. just in case you forget, leave this object at the bottom of the sprite.