Hi Susanna,
an array is one of the most important construct in any programming language - so you should be looking at it.
Anyway, the pictures themself have to reside in a movieclip.
Depending on how many pictures you want to have on stage at once, you need the containing movieclips, or loader components.
You create either an array, or an XML-Structure for storing the picture names, paths etc.
If the reside all in the same path, it is easy, because you only need the filenames then.
picList=Array("filename1.jpg","filename2.jpg","filename3.jpg"); // as many you like
so far the array.
Now you assign the filenames to the loaders - or at least as many as can be displayed at once.
If you want to shift to the left, you move the second picture to the first loader, the third to the second etc.
If you want a more smooth move, just make the loaders x-coordinate chnage, until they overlay in position, and then do the move of the pics.