In short, you can't. In the default Database, only England down to BlueSquare N/S are playable, which means only leagues down to that layer will load. The teams will exist, all the way down a long ways. Game just rolls dice on which teams go up and down in the non-playable/non-loaded leagues. Also means you can't play a team until it hits that layer.
Now, you can always go find yourself a database out there that is set up lower (I'm using one for my FC United save that went down to layer 9), use that to start the game, and you have access to the Divisional leagues. But yeah, the default D-Base only goes down to the end of Conference.