Please just calm down
I will try to explain it by equaling it to units in other mods
Army=Army (explains itself, it consists of regiments in our case)
Brigade=Regiment (it consits of several companies, just like brigades of regiments)
Company=a part of regiment
Its just like any other mods=someone creates an Army, then people form Brigades (Regiments in our case) and then people create Companies. For example:
Player A decides to create a company, named for example Captain Ffoxe's Company of Foote of Kings Lifeguard (Red is his rank, Blue is the name of company, usually it was named after commanding officer of the company,indicates what sort of unit it is,the name of the regiment
Then more people like Player A create another (around) 9 companies (there were usually about 10 companies in total in each regiment)
Player B then chooses to create a regiment, uniting all those 10 companies into one whole unit (basically its something like a brigade)
Then there are more people like Player B who create another regiments
Then Player C decides creates an Army, for example Earl of Essexs army
Then regiment leaders can join those
I hope I explained it well (there may be some mistakes)