[1.7.10] Adding a function to an already existing item

[m4++]

I used to code minecraft mods using modloader back in beta, and haven't ever since. Now I'm not used to this whole minecraft forge thing. I've already started learning, but that's not what this is about. I recently got back into it because I wanted to create a convenience mod, but I can't find how to do it anywhere in minecraft forge.

 

I want to create a mod that places a torch(from your inventory) when you right click with a pickaxe. All that I'm asking is if there's some kind of reference book for modding like this or if I'll have to keep on learning until I can figure it out.