How to use equipment items?

[Kitty]

I got the bomb item a while back and didn't pay close enough attention to the tutorial message at the time, and there seems to be no usage tutorial past that. I reconfigured the keybinds a little bit to my liking, so Z is melee, X is ranged, C cycles items.

How do I use it? It is equipped in my menu, and appears at the top.

[GespenstKAF]

Hold down your ranged button so it charges, then press your melee button when the charge hits its peak