The answer depends on a number of things:
Do you solder your rail joiners? How many trains do you wish to have running at one time?
Initially you can just connect a pair of wires from your command station and see how it goes. You won't hurt anything.
You may find that in some places you don't have power because of your rail joiners not making a good connection (which is why many folks solder them).
If you wish to have power fed to your layout in multiple locations that is easy to do.
I solder 18 gauge feeder wires (one red, one black) to my track and drop them through small holes (one hole per wire) drilled just outside the rails between a pair of ties.
Then under the layout I use 3M "suitcase" connectors (Scotchlok™ 905) to connect the feeder wires to my "bus" wires.
The "bus" wires are just a pair of 14 gauge wires (one red, one black) that start at my command station and then run under the layout from place to place as needed to connect the feeder wires.
You could "zig zag" around under the layout running from feeder wire location to feeder wire location or you could run the bus wires straight down the middle of the layout from one end to the other and then use feeder wires long enough to reach the bus wires.
When doing this be sure that you are consistent in wiring all of your red feeder wires to one rail and all your black feeder wires to the other rail.
If you find this confusing you can just take a car and temporarily mark in some non-destructive fashion one side as "red" and the other side as "black". Then you can push the car around you layout and observe at each location where you plan to have feeder wires to verify which rail is on the red side and which rail is on the black side. Of course when doing this you must not remove the car from the track.
Do you have any reversing loops? These take special consideration.
There is no one correct way to wire a layout but there are many little things that need to be done correctly to have a layout that functions well.
