Newbie question

[Cryptotec88]

When you hit "c" or the Colonize button then click on the planet you want to colonize, the game automatically loads 4M of your people and then sends the ship off to the destination. At least that is the way it normally works. (Works great for me, full or demo.)
You can load the colonists yourself by clicking on the colony ship then hitting "T" or the Transport button and loading the colonists onboard yourself, then telling it to colonize the planet.

Cryptotec88