I use Furkot.com to build my routes. It's pretty easy to use.
If I don't upload the GPX to my Boom Nav I will use an app called Scenic.
If you create an account in Scenic and Furkot (use your email address) you can open your Furkot routes in Scenic and use the navigation option. Scenic is free for the most part. I have been using them both for a couple years and decided to buy a year from Scenic so I could try everything out. So far I am liking and it is worth it.
Hope this helps.