It works exactly like skill works in terms of effects on ones combat abilities for the hand it is equipped in. For instance, you are using a Great Sword, two handed weapon, as such it effects all attacks, if it were one handed like a sword, it would only effect your main or off hand depending on which you had it equipped to. The skill does not pop up in the combat skill menu because technically in the case of one handed weapons, you have two skills, one for your main hand, and one for your off, also, this way it does not impact your ability to learn WSs, activate quests, or so on. The only thing this skill really does is give you the Attack/Accuracy that skill normally does.