You still need to place your components with some thought, an autorouter is not capable of making amends for a poor layout. Laying out a board is an iterative process - place some components, arranged logically, rotate, move and rearrange to minimise crossing tracks on your rats nest. Rinse and repeat. Think a bit about where your connectors/switches etc sit. Depending on your board, there may be other issues - capacitance/thermal issues/RF all of which may need to be thought about. Just plonking a pile of components on a board and expecting an autorouter to sort out the mess and join them all up with correct sized/length/capacitance tracks is doomed. For a very simple design, it might come up with a solution or an autorouter might help you with parts of a very complex layout. You will probably learn far more about the process of laying out a board by not using an autorouter.