Squeaky floors are a VERY common problem. To understand the 'fix', you need to understand the cause.
Most builders, in the name of time and $$$, nail the sub-floor to the joists. And, they don't use a glue to help with adhesion. Over time, the nails work loose and you have squeaking. When the floor is covered with carpeting or hardood, or you don't have access from underneath to make the fix, your job becomes a bit more difficult.
In short, in your case, you need to try and find the joists. When you do find it (or them) and install the screw, it will pull the sub-floor tight to the joists. Then, your squeak(s) will go away. If you can't find the joist by knocking or measuring over every 16" (assuming the joists are 16" on-center), you'll need to do your best to guess where it/they is/are, and install a screw. If the squeak is still there, move left or right about 1" at a time, and screw again until the squeak is gone. I'd PRE-DRILL your holes but BE CAREFUL you don't bind up a lot of carpeting in the drill bit! Do your best to 'move the fibers out of your way. If you're good at it, you may be able to 'feel' that you're drilling through the sub-floor AS WELL AS INTO a joist. (You know, if your sub-floor is 3/4" thick and you drill 1" where all of a sudden, the drill 'gives way' through the floor, you know you haven't hit a joist.) A contiguous 'drilling sound' or 'drilling feel' would be a good indication that you hit the joist.
As an added aid, if you can see the sub-floor in your closet, you can see if you can 'determine' where the joists are. If the floor is exposed in there, start measuring. The nail lines will tell you how far apart the joists are. Just 'translate' that info into the main bedroom. My closet floors are carpeted but are NOT 'tacked' down. (I can remove the carpet by simply lifting it up.)
I'm not sure what type of Kits the Home Centers have but you need one that will 'work' through carpeting. At worst, try Squeaky Floor Links for more info on parts.