Zorg Empire

I am new and you probably are tired of answering n00b questions but I would really like to know so I don't spend the few resources I have on something that wont help me expand.

Also there is a guy that has been away for a month in my (area?) how do I take over his planet? (It has a moon is why I want it)

You build a colony ship and send it to an empty slot. You can look the requirements for colony ships under Technologies in the Empire Menu on the left of your screen.

Also, there is a Help section in the forums for post like this.

Just a side note here, you can't take over other people's planets. It has to be an empty slot.