Your layout doesn't really need a bus, but since you have it set up already, no biggie.
The bus in an electrical power distribution system is the first order of power delivery after the power supply. It would be the heaviest gauge of wire, the thickest.
The idea is to use a large cross-section and commensurate surface area of that larger wire to provide an easier path for the electrons. Means less resistance, so less voltage drop. As you add length to any gauge wire, you then incur more voltage problems. So, it's a combination of heavier wire and greater length up to the point of not making much sense any more.
After that, you tap into/onto the bus here and there with lighter gauge feeder wires which do have a lot more resistance, but their short runs help to overcome that problem...so again, not so much voltage loss.
As stated, your two heavier gauge bus wires issue directly from your controller unit.
I would have to agree in principle with the suggestions that you might be further ahead generally in the hobby to spend more time learning what you are trying to do. For you to be this far advanced in the process and not know what you are doing electrically seems a bit careless to me.
-Crandell
Have you read the manual that came with your system?? It should explain the basics of how to wire up your layout and where to hook the wires to.
The bus wire has to start at your DCC controller's power output. You can run it in a 'T' from your controller if it is near the center of your layout, or just in one direction if your DCC system is near a corner.
If you're so uneducated about wiring, you need to start here:
http://www.wiringfordcc.com
I am starting to wire my layout for dcc. i understand that all the feeder wires have to connect to the bus wire but i dont know where to connect the bus wire to?? do i connect it to my controller? my layout size is 8ft long and 2.5ft wide. i am doing a N scale layout. How do i start? what do i do first. please list in steps because i have never wired a layout before. thank you