Colonists may be dispatched from the main map in one of two map modes: the normal map mode, or colonization map mode. Colonization map mode may be turned on by clicking the colonization map mode button (it shows an icon of a small blue ship) in the left-hand-side interface. In colonization map mode, the colonization screen is displayed whenever you select a non-city province. It will display the chances and costs to send a colonist or a trader. You can also send a colonist in normal map mode, by right-clicking on the province and selecting the appropriate menu option.