The windage IS adjustable at the front sight. You'll see that the front sight post is offset from center, so as you turn it, it moves from left to right. Note that there's a set-screw you have to loosen before you can turn the front sight post. Also, you'll either need a special tool, or use a fine pair of needlenose, or forceps, or something similar.
The routine for sighting in the irons is:
1. adjust up or down to get elevation right.
2. The adjust left or right a half-turn or less to get windage right.
Another thing to note is that some of the rifles are not assembled by Century Arms entirely straight, and you may not have enough windage to get on target. If that's the case, you have some options:
1. Return it to Century and get one built straight.
2. Modify the front sight by grinding off the post, drilling a hole and using a piece of drill stock to put in a new post with more offset. That's what I did (or rather, a 'smith did for me) and it worked well. The finer post gives me slightly smaller groups. You'll find the rifle is quite accurate.
3. Forget the irons and just scope it. Not a good option, but some do that. There are a number of aftermarket scope mounts. I got one that clamps to the receiver scope mount pads, and sits low enough on the receiver that when a scope is NOT installed, you can see the irons over the mount. When the scope is mounted, its nice and low to the bore axis, too. Not like the claw-style mounts that you sometimes see. But you'll have to google that mount up, since its been over 5 years since I bought it, and I don't have any records.
Hope that helps.