How does Aspect of the Cat work?

I just got my Farrul's Fur body armour. Something for my Cyclone Slayer (very normal build). I expected to see the Aspect as a buff, like a charge or something, being activaded just by wearing it. So far nothing happens... works as a regular item.
Is there something I'm missing? Must I do something to activate the buff?

It's two separate buffs that alternate. You should be able to see which one is up at any given time.

As GreyLensman say, you start getting the buff by just equipping the item with Aspect of the Cat on it... And, of course, activating the buff.

After that, the 2 buffs will start alternating - it's similiar to Auxium, Vulconus and Arborix - except there is an actual graphic tooltip in the top-left corner of positive effects on you that can actually tell you which of the buff is actually active.

you need an item that grants Aspect of the Cat skill. Then you activate the skill.

Aspect of the cat is pretty much like an aura that affects only you: only has effect after you activate it, you see the rolling circle on skill if active, like any aura skill, and you see which buff is active on top of the screen.