If you press ALT and type WIN, you will get a new option on the menu bar.
When picking a country, go to the very bottom of the screen beneath Spain and click on the top of the red box.
To sell boycotted things, press select item and press U.
Try to provide each colony with a carpenter, lumberjack, statesman, and priest along with a miner, blacksmith (for a supply of tools), and soldier (with cannon).
Click here for some more hints from PC Gamer Online.