By default the planner orders your stops for the shortest overall drive. You can also pin where the route begins and ends.
Start point
Put the postcode you set off from - usually your depot or home - in the Start box at the top of the planning screen. The route will be ordered out from there.
End point
Use the End box if you need to finish somewhere specific, like back at the depot. Leave it blank and the route simply ends at your last delivery, wherever that falls.
It’s remembered with saved routes
When you save a route, its start and end points are saved with it - so a round you run every week comes back ready to go. See Saving a route and reusing it weekly.