In Outpost 1.5, it's best to send the resources needed to the old command center via the transfer interface (using the trucks/routes etc). I don't remember if you have to do it that way. To build the second command center, you must build it on uncleared land like you did with the seed lander (yes, I know it doesn't make sense). I discovered this by accident after messing with it for awhile. Note that you select your active colony by right clicking on the appropriate command center. You may transfer colonists from one of the dialogs (either from right-clicking the command center, or in it's own box). Make sure to get CHAP, etc running quickly and have enough colonists there, or it will die permanently or disfunction. Also make sure not to bulldoze land with one colony and build stuff with another, as they will fail to get LifeA/LifeB (air) and other resources and not build or function. I believe you can solve this by bulldozing using the right colony, but it can mess things up, so leave lots of room between colonies. They cannot be connected. There basically is no point to doing it other than to have fun or let the AI run amock building stuff diagonally (and it can build in places you can't, like out of normal range or on the edge of the map!)
I personally enjoy trading with the rebel colony for things you can't normally get, but you really have to work to stop from them coming to your side (lots of hostile police). It's also good to memorize the techs required to get nanotechnology, so you can stop mining (really, it gets ridiculous to get explorers to find new mines fast enough as you grow). Of course, you get MPG from recycling, some points (equivalent to any resource) for every residential building. I suggest building in a pattern that allows a solid block of residential units.
This was the first game I really got into. I was about 10 at the time, and I went over ways to redesign and improve the simulation it in my head (like better population modeling). I have finally begun re-programming Outpost to fulfill this desire (today is my birthday - I am 24 now!) I will post another thread about this project.