Under Army is where you can see costs and strengths of units, as well as produce and dismiss units.
Units are built in much the same manner as crafting items, except they require a Barracks for housing and an available worker is needed to transform into a solder (which immediately removes him from his housing and turns him into a “crafting process”, as part of cost of that unit, just like the other material costs).
For the “crafting process” of the soldier to progress a Training Square is needed, which also requires a worker to be assigned to it to function.
Moving units is done on the World Map though.
Keep in mind that units have an Upkeep cost, which is paid once every 30 days.