- Make a new thread
- Include the region/country/state/province/other useful location information in the thread title
- Include some indication of whether it will be a one-time deal, or a recurring event
- Include relevant date information in the thread title if there is room
- "USA, Illinois, Chicago, West Loop -- Recurring Study-Group First Sunday Every Month 2 PM"
- "France, Paris, Bastille -- Meetup 15 July 2014"
- "Tinychat Study Group Every Thursday at 12 AM GMT"
If you have no idea where or when would work best, nor what type of event it should be, post an open thread, and change the title (by editing the first post -- I recommend reserving the first post as a "central" repository of any information you collect regarding the event) once that information has been decided upon, for future clarity.