At the very beginning in the game, you only control one star system, as you develop, and you accumulate enough Culture Points, it is possible to expand your empire from the Wealthy Mars to the mighty Superearth beyond your system through Colonization.
Prerequisites
To successfully colonize other planets / star systems, you need:
- A few (at least 3) Colonial Spaceship
- Enough Culture Points
Your level of Culture Point and the requirement for the next planet / star system can be checked at Empire Overview (Next to Notification) -> Planets
Alternatively, you may check the formula of Culture Points required for those by visiting this page.
How to Colonize
To successfully colonize another planet / star system, you must first designate a fleet consisting of only Colonial Spaceships. Then, just as you would do it in other scenarios, send your Colonization fleet to your desired planet / system. The Game tells you if you have enough culture points for the colonization, and, in case of colonizing another system, the duration for the Colonization fleet to arrive, because the Colonial Spaceships are "rather slow".
NOTE that when you colonize another system, you always colonize the first planet of the system (i.e., the Planet of Orbit 0), and most likely, you are gonna start with a Minor Metallic in your new system.