It doesn't come with instructions, but it's not very complicated.
You insert the first balloon (with plenty of lubricant) and then slowly expand both the inner and outer balloons (only as much as is comfortable for you) by squeezing the inflator pumps. The nozzle creates a tight seal and you can completely relax while taking your enema with no leaks.
When you're ready to expel you should remove this nozzle over the toilet until you get used to it. Make sure the inner balloon is completely deflated before you remove it.
Depending on how much 'anal experience' you have this nozzle might take some getting used to, but it is by far my favorite.
If you happen to be really impacted it would help to take a small enema before inserting this nozzle to make things easier - but this isn't usually needed.
Also, I find that taking a bit of water before inflating the inner balloon helps prevent discomfort.
If the double balloon nozzle is too much for you to take (or if you don't want to spend $150) this nozzle will also work great:
http://www.enemabag.com/photos/520-2.jpg
Optimal Health Network sells that one. The double balloon nozzle is a lot more fun though π and it will last much longer.