A complete review can be found here, but basically, you can't. CS4 was the last version that was able to generate INX - the format was replaced with IDML. You must export IDML with CS5.5, open that IDML in CS4, then export INX from CS4.
Why do you need INX? If it's for someone with CS3, then that person may not get a useable file, if any features introduced after CS3 were used in the CS5.5 document.