When you've launched the app, it will automatically define your current location and mark it with a blue dot on the map.
You can then enter your destination address in the search bar in the bottom of the screen, or — set it with a long tap on the map.
By long-tapping anywhere on the route, you can add a via point (available in Premium mode only), or select the tapped location as the route start or destination:
Sometimes, when there is more than one way to reach the destination, the app will suggest alternative routes (colored in paler shade of blue). Tap on it to select between the suggested routes: