How can I fix my Troybilt lawnmower?

Model Number: 13AV60KG011
Serial Number: 1C058H20539

The Troybilt Bronco riding mower (18 HP Kohler Courage) will not start. I installed a new battery but it still will not engage the starter. I have followed the starting procedures, parking brake engaged, in neutral, PTO off, etc. The head lights will not even come on when the ingnition switch is in the on position. It is as if there is no electrical power to anything. What is holding the start circuit out?

Thanks,
Tom Hoffman