Next up in the Mayor role, which allows you to obtain colonists to man your plantations and production buildings.
There is a small card called the Colonist Ship which contains the colonists. At the start of the game, a predefined number of colonists is set aside for use in the game (the more people, the more colonists). Then, one colonist (not from the set aside supply!) is placed on the colony ship for every player playing.
When you choose the mayor, you take a colonist from the ship. Then, the next player takes one, and so on around the table, until all the colonists have been taken. This means that if there are more colonists than players, some people will get multiple colonists.
Next, as the Mayor, you get to take an extra colonist from the supply if you want to.
Following this, everyone gets a chance to place their colonist on their buildings. They are also allowed to rearrange the colonists they already have. Remember that only plantations and buildings with a colonist on them are considered "active". Any unmanned building is just taking up space.
The last job of Mayor before he gets fired is to count the number of empty colonist spaces in the building section of every player's board, and put that many colonists back onto the colony ship for next time. If this number is less than the number of players, it gets bumped up so that every player will get at least one colonist next time around.
The important thing here is that the number of colonists placed on the ship is primarily controlled by the number of buildings people have with no colonists on them. Since you get to move your colonists around, you can influence the number of colonists there are, perhaps to set yourself up to be the mayor next round and obtain more colonists.
The ability to move your colonists around also helps you change things mid-stride, like deciding to produce different goods, or stop producing a good so that you can put a colonist on your quarry, and so on.
At the end of the Mayor's turn, if there are not enough colonists left to fill up the colony ship, the end of the game is triggered. Play continues until the next time the Governor card would move to the next person, and then the game ends.