Youll need to mount them somehow.
Screen top wedges are the easiest and likely the cleanest way to go about it.
You can make them yourself though. There are also other ways.
You can use a 1/4" drill bit to put a hole through the frame.
This allows you to push the line directly through, into the cage.
You can then use straps to attach the line to the inside of the frame.
Something of an example may be seen here:
http://s618.photobucket.com/user/davidfishman/library/Cage%20Build?sort=2&page=1
As far as positioning goes, I point them at foliage thats been placed at the very top of the enclosure. This still blows the fine mist all over, but it will collect on the foliage, and "rain" down. For the animal to drink, most need more of a rain, than a fine mist. The fine mist is better for cooling things down, and wetting a larger surface area though.
EDIT: Youll also need to secure as much of the line running from the pump, as you possibly can. The diaphragm pump doess not put out a steady stream, but a rapid secession of bursts. This causes the line, pump, and cage to shake. If you secure the line though, its almost unnoticeable.
