How do you transport land units by boat in europa universalis 3

Of course you must have transport ships in your fleet and you need to have enough capacity to transport the number of troops. (A 5 troop army will refuse to attempt to load onto a fleet with only 4 transport capacity). Move the fleet to sea in the coastal territory next to the army (you cannot load a fleet that is at anchor in a port). Move the army into the same coastal sea territory. They will board the fleet.