Zoom into the section of the route and click where you want to drop a pin. It will load a default question mark pin that looks like this:

If you dropped the pin in the wrong spot simply click Remove Pin. If you're happy with the pin location click 'Choose pin' which will launch the pin types to choose from:

Choose your pin. The next screen allows you to rename the pin e.g. change Transport to "Taxi rank" or 'Pub' to 'The King George' . Flesh out the description in more detail and why it's on the map. Add an image if you have one available and is relevant to the pin you've chosen. Once you've done that click save and the pin will be on the map. Simply follow this process for all pins you believe need to be on the route map.