This dialog gives you access to all the tools you need to be able to build ship-depots and docks.
In the top-left hand corner is the dock building symbol. Click on this to change the cursor to an image of a dock. Docks are used to allow ships to pick up and drop-off cargo and passengers from nearby industries and citys. To place a dock click on an edge of land, this will build a two-tile dock. They must be built on a straight edge of land. You are able to build very large docks, they can be as wide as you can make it, but the docks must be directly adjacent to each other. To schedule a ship to a dock you must send it to a square that is directly adjacent to any part of the dock, not to the dock itself.Beware, docks cannot be removed properly yet!
On the bottom row there's two symbols, both for building ship-depots, they are only different in the fact that the one of the left-hand side faces the left, and the one on the right faces the right. Click on either of them to change the cursor into an image of depot. Depot are used to build all the different ships that are available. To place a depot simply click on the water-square where you want it to be placed.