How can i attack enemy planets/systems to take control over them?

I have a fleet (with a colony-ship) orbiting his system what should I do now?

Hope this isnt a bad question =(

This is a common question. You don't need transports or colonists. Any fleet will do. When you have a fleet orbiting an enemy outpost/colony, look in the lower left for the control buttons. You will see one with two fists, the hover help says "start invasion". Click that. Then you "should" get a progress bar on the system which advances to show your ownership. It will update each turn. Some techs such as HE Missiles (S2G Kinetics) make it go faster. There may be a bug; sometimes the progress bar does not appear. Once the progress bar shows 100% you own the system.

oh i have a bug. Thanks to you i foundet the button which is completly invisible. The only way to see that button is to hold my mouse on it (without picture but with tooltip). I think I will post that tomorrow in the bug threat.

Anyways thanks to u =)