A Step can have only one default location defined where a Record travels after work is complete in the Step. Conditional Logic, called Edges, can be created to route work based on predefined rules as described in the Working with Paths article.
To set default Step routing, start from the originating step, press Shift+Click and while continuing to hold the mouse button on a Step, drag the mouse towards the next Step in the Workflow. An arrow should emerge while dragging.
Once the Step changes color, release the mouse. An arrow will be created which now joins the two Steps.