Specify a desired route to the navigation

I usually do this by adding one or more intermediate "destinations" that happen to be along the route I want to take. An easy way to do that is to add a destination by picking it on the map, somewhere on the desired road.

When you do that, of course, your distance-to-go and ETA are showing just to that next intermediate "destination" by default, though you can press that distance/ETA icon to expand it to show the whole sequence of distances/ETAs.