Portable Bronze MortarFollow

I made one of these (Portable Bronze Mortar) and it says it has 8 charges in it, but I cannot figure out how to use it or activate it etc. When I regular or right click on it I do not get the green circle targeting thing I get with my other explosives etc? Can someone please, please help me figure this out? Thank you!

I had it on the toolbar and apparently that is why it wouldn't work. I right-clicked on it in my inventory last night and it worked fine but never would work when I would right click on it on the toolbar.