How do you make a unit in Civilization IV?

Answer 1

A window should pop up when you create a city asking you what unit you wish to build. Select which one and the city will build it. If you want to change which one you are building, select the city and change it in the management screen.

If you want to combine multiple units into an army, move two units onto the same tile, click one, select-join all units into army* (usually depicts three men in DIFFERENT colored clothing standing together) and they will combine to move and attack together.

*If you click the button with three men standing together wearing the same color, it will only combine units of the same type such as only combing archers and leaving out swordsmen ect.