How do I make apertures in photoshop in the shapes of letters and numbers?
You use a text mask.
A few tutorials
http://www.online-photoshoptutorials.com/2008/04/text-masking-image.html
http://www.newearthonline.co.uk/article/233
http://www.photoshopessentials.com/photoshop-text/text-effects/image-in-text/
http://www.photoshopessentials.com/photoshop-text/text-effects/texture-text/
OK, so you do the same thing, but additional masking is required for each different letter.
You unlock the underlying layer(s) and move them around. It's still the same process, you're just doing it for each letter instead of the whole word.
Or make a single layer filled with colour e.g. white, add text, select it then delete it cutting through the layer, then wave your other images around beneath it.