Map- from point a to point b

Hi everyone,
I am trying to build an app that shows safe routes. In the app, the user must be able to put in their location and where it wants to go and the app will show it a route. I have put in the google maps API key but, it only shows a map and does not allow the user to put in their destination and it shows the route. Is it possible to build an app that does this and if so how?