"So how do we coordinate, drop my phone here or?"
General process is to stir the waters in "planning" - you're on the right track with this thread. Once the basics firm up (what trail, where to meet, when to meet, who's interested) in "Planning" someone (you most likely as you started the planning thread) does two things - starts a thread in "Planned" with those basics and - of most important - places an event on the calendar. The calendar event creates the run in the "yellow box" near the top of each web page. This yellow box / calendar / RSVP run entry allows people to RSVP. You should RSVP for your run. The folks who were interested in Planning RSVP as well. Others in the group might RSVP a Yes as well. Done!
You're at the point of firming up the basic details for this run. Once those are known - Planned and Calendar happen.
PS: Once a "stir the waters" run firms up in Planning, the Planned and Calendar entries happen. Some folks ask - what's the purpose of "Planned"? The idea behind Planned is to have a mainly clean thread for last minute items. The Planning thread is often littered with posts (much as this post will be) making it harder to see the important details of a run. The Planned thread is often one post to a short handful of posts - the last minute stuff - sometimes people saying "I'm running late" or "last minute broke down - can't make it". Once Planned is created, it's recommended for folks to ignore the Planning thread and do the last minute stuff in the Planned thread. The person who creates the Planned thread might / should / it'd be nice make one post in Planning that has the URL to take folks to Planned (helps herd folks to Planned). Nothing's set in stone. We're a self-serve group - get it done and all's well.