NORMAL Mode: The default state of the board is NORMAL mode. Moving over a hex highlights it, and clicking on a hex will give you a description of itself (e.g. "Hex #20 (roll=4) is a lumber resource").
ADDSETT Mode: To add a settlement, choose the color you want and click the "Settlement: Start/Stop" button. Then move the mouse over the intersection where you want to place it. If there is already a settlement or city there, or if you are too close to another settlement or city (there must be one empty intersection between two buildings), or if you are not placing your settlement along a road of the same color, your settlement won't appear, and you can't place it. The first settlement of each color can be placed regardless of roads.
To place the settlement, simply click the mouse. To cancel building a settlement, simply click "Settlement: Start/Stop" again.
ADDROAD Mode: To add a road, choose the color you want and click the "Road: Start/Stop" button. Then move the mouse over the edge of a hex where you want to place it. If there is already a road on that edge, or you are not building a road adjacent to a settlement, city, or road of the same color, your road won't appear, and you can't place it. You cannot build a road at the end of another road segment that ends at a settlement or city of a different color.
To place the road, simply click the mouse. To cancel building a road, simply click "Road: Start/Stop" again.
ADDCITY Mode: To add a city, choose the color you want and click the "City: Start/Stop" button. Then move the mouse over the settlement of the same color you wish to replace. If there is not a settlement of the same color there, your city won't appear, and you can't place it. Cities replace settlements; you will get a settlement back when you build a city.
To place the city, simply click the mouse. To cancel building a city, simply click "City: Start/Stop" again.