When you drag the sigil to to the bow, it should give you a pop up showing your torment sigil and 1 unused upgrade slot. Are you not getting that?
Sigil of Perception gives you increase precision every time you kill something in the same way Sigil of Bloodlust gives you power. There are several types of these “stacking” sigils. You can only have 1 effect active at a time. But this doesn’t look like your problem. You would be able to put the Bloodlust in, you just wouldn’t get the effect if you had Perception on swap and already had stacks up.
