Bridging works just the same as any other transport move. The only difference is that the transports do not leave the seazone.
So for transports in a turn you can on either the combat or non-combat movement phase:
A) all units are from the same power:Optional: move your transport load 1 or 2 units (out which at least 1 is an INF) from 1 or more adjacent land areas in a friendly SZ Optional: move your transport Optional: in case in step 2 you loaded only 1 unit, load a second unit (again if you have 2 units at least 1 needs to be an INF) in a friendly SZ Optional: move your transport (end in friendly SZ) Optional: unload units into 1 hostile area (amphibious assault) or 1 friendly area (non-combat reinforcement).
Note in all the movements the transport can not exceed the maximum number of movements it has (so standard 2, when departing from a friendly harbor 3).
Note the transport movement is completely optional so bridging occurs when you don’t move the transports at all.
You can only use a transport once per turn, so you can’t do an amphibious landing and in the same turn reinforce the land area using the same transport. Obviously you can reinforce it using a different transport.
B) When the transport belongs to a different power:On your turn load the units into the transport _Optional_On the other powers turn move the transport On your next turn unload into an area.
Note you will always have to wait one turn when loading and unloading using a different powers transports. So even when the transports don’t move you can not load and unload on the same turn using a different powers transports.