Brigades are actually loaded onto a fleet (see section 6.7 & 6.7.1 in rulebook), you cant load a brigade onto a single ship.
Example: You have 4 brigades and a commander in one of your shipyards, which you
In section -20- of the turn sheet, using the command E.(brigade number).15 for each separate brigade (not the federation number), and the command E.(commanders number).any ship in fleet 15 (you must specify a ship i.d. number for the commander to board). Brigades will also board a fleet that is situated adjacent to the land co-ordinate the brigades are on (i.e North, South, East or West) using the E command alone - no boarding direction needs to be specified!
With the brigades and commander safely on board move the fleet to the desired location.
Example: The fleet has berthed at another of your shipyards.
In section -20- of the turn sheet, using the command 9.(brigade number), and command 9.(commander number), the troops and commander will disembark onto that co-ordinate. If the fleet was on a co-ordinate adjacent to the coast, and not in a shipyard, instead of command 9 you would use the unload commands 1-7 (see section 6.7.Boarding in your rulebook) and they would land on the coast.
When troops are disembarked onto a co-ordinate they do nothing that month except climb off the ships and stand on the beach. Unfortunately they cant conquer any territory or participate in any battles, unless a battle is already taking place on the co-ordinate on which they land. To conquer the co-ordinate next month they must be given a 9 1 movement order, i.e move while remaining stationary (see 220.127.116.11).
The quantity of troops that is listed as being on board a fleet is actually the tonnage of troops on board that particular vessel rather than the number of soldiers. So you can rest easy that the remainder of your troops aren't swilling down wine at his majesty's expense at the embarkation port!
One other point - if the fleet on which your brigades are being transported is involved in a sea battle you may lose some of the troops within the brigades, this is especially relevant if you lose a ship which has part of a brigade on board. (even though your brigades might appear to be at full strength on your turnsheet, while still onboard the fleet, the true headcount will only appear when they are disembarked).