How you setup the route depends on what you are trying to send. For Dash to my server’s route I created a topic and its route sends the data as a variable in the URL request:
Where “decdata” is the decoded data from my Dash. In this case I create colon separated data of “temp:volts:count” and a topic of “T”
Pushbullet’s API looks to be JSON based, so you’d use https://api.pushbullet.com for destination and then either compose JSON in the Post using variables or use ‘decdata’ if your Dash is already sending the properly formatted JSON.
This page has a pretty good breakdown with examples: https://hologram.io/docs/guide/cloud/data-router/
I haven’t used it before, but you’ll probably need to set up an authorization header in the route and include your access token for pushbullet.