I've started to make my own maps.

And while I remember it was a bit tempermental, what I'm finding is that I don't know how to add the values of Grain/Material/Essence to a map. So that I can decide what is a 4/2/3 or whatever.. 

I found a "Mod" option in the drop downs that allows me to in theory put something with essence down from 1-9, but when I click on it nothing happens.

One I'm assuming I'm not clicking correctly, probably something along the lines of control left or right click.

Could someone please enlighten me on this subject. (Pictures would be a super plus, and a youtube video would be amazing!)

Thanks for any help on this front that anyone can share.