What does the car do when you turn on the ignition?
If the engine cranks but won't start, you should first investigate the fuel supply to engine. Check fuel pump. My brand new Sorento developed this problem after few months, engine would crank but won't start. It turned out to be fuel pump failure, mechanic said its due to contaminated fuel.
If the engine doesn't crank but the battery, starter and fuses are good, there could be several causes and its difficult to diagnose. For example, immobilizer error, faulty ignition, faulty ECU, etc.