how do i check it?

How do i adjust it?

Can it be adjusted?

Need some info.

You need at least a Go, and NO-GO gauge, and a FIELD doesn't hurt.  You can check it yourself but it is really not adjustable.  It is set from the barrel maker when they put on the barrel extension and once the gas port has been drilled, it is pretty much a done deal.
Should you find that it closes on a Go and not on a NO-GO, everything is fine.  If it will not close on a GO, your chamber is too tight and some ammo may not chamber correctly.  My AR pistol was like this.  To fix it I swapped around bolts and the very second bolt I tried it closed on the GO, and not on the NO-GO, which is what you want.  If it is too tight the chamber can be cut a hair deeper without too much trouble.
If it closes on a NO-GO also, then it really should not be shot.  You can try switching bolts around like I did and you may find a bolt that will be just enough different that it will adjust the HS enough to close on the GO and not on the NO-GO.  
If you get one that closes on a FIELD, that barrel is trash unless you are an exceptional metal smith.  To correct that problem, or even the problem of closing on a NO-GO if swapping bolts does not help, is more expensive than a new barrel unless you have friends in high places.
To fix, the barrel must be removed from the barrel extension and two or three turns taken off the threaded end so that the chamber can be re-cut and a new indexing pin installed.  One turn may not allow a new index pin hole to be drilled but since I am no metal smith, maybe a good one can do it with just one turn taken off.  And if your barrel is exactly 16 inches, you are going to end up under the legal minimum.  If you do have extra length you can afford to lose, the trim job has to be exact so that when the barrel extension is reinstalled and properly set, the gas port will be in the 12:00 position, and that can take a lot of trial and error, and can be very time consuming.  Then the chamber has to be re-cut and the headspace set.  All that makes it more simple to just buy a new barrel.  Plus, if you have a chromed chamber, re-chambering is going to remove some if not all the chrome from the chamber and throat and that opens up a whole other can of worms.
Adjusting the headspace, unless you can do it with bolt swaps, is not a job for the average do it yourself-er.

thanks thats just what i needed

Make sure you know the proper way to check headspace.  You don't just drop the gauge in the chamber and let the bolt fly shut.....

True that.  They should come with instructions, all mine did, but if not post back and we will fill you in.

new bolt & new barrel ? Don't waste your time checking headspace.

Headspace checks are a scare tactic by people of a certain age...or barrel/bolts of a certain age :)

lol

Unless you shoot 100,000's of rounds a year like a basic training m-16 or something...