Hi Hugo!
Welcome to the forums!
It seems you haven't still get hold of the division formation process and how to work with stacks dragging them aroudn or meging them draggin one on top of another or better still, using the tabs over the unit display.
My best recommendation woudl be to do again the tutorials very carefully. They explain the process step by step, better than i could
Its very important to you to get the difference between, units, divisions (a special kind of units composed of smaller units) and stacks, which are the playing pieces you move on the map and that are composed of units/divisions.
Once you get this straight, all will make sense
Also i recommend you to take a look at this excellent forum tutorial
http://www.ageod-forum.com/showthread.php?t=7475
It offers you great tips on how to organize your forces aroudn for best effect.
Cheers
PS: you don't really want to put wagons on divisions. Its better to use only combat troops on divisions and put the wagons on the same stack that the divisions, but not inside them.