You should have at least one resource-user (i.e. a user attached to a resource, generally a vehicle). Head to Settings -> Routing and pick it from the list.
Fill in the start and end address. These are the start and ending points of your routes for this user. They can, of course, be different. Then choose the start and end times for the user. If your driver or engineer works 8 hours per day and starts at 07:00h, you should enter 07:00h as the earliest start time and 15:00h as the latest end time. You might want to fix a maximum driving time for your driver or engineer. Then move on to the GPS tracking schedule: it should cover at least the working schedule defined previously (from 07:00h to 15:00h, in our example). You can also specify which week days you want to track your user. If you're using skills, you must enter them here. Skills are your user's abilities to perform a certain service. You'll need a Plummer to perform a Plummer's job or an air conditioning engineer to fix or install an air conditioning unit. If, for instance, your user is able to do both, you would enter "plummer" and "air conditioning" in its skills field.
Done. Your user-resource is now enabled for routing. This means that you'll see his start/end position in the map and that routes will be automatically calculated for him once you've entered or imported new visits.