I don’t think you’ll find a quicker tutorial anywhere than this one from Benjamin Warde on how to sync the collection of your choice with Lightroom CC for your Mobile Device (all in less in 60-seconds).
By the way — Even though you may be using Lightroom Classic, the Lightroom mobile app is called Lightroom CC (don’t get me started). Anyway, here’s how it’s done:
This day has the possibility to be super-awesome. Let’s do this! 🙂