How do I set a Google reminder?

If you are asking how you set up an event so that the guests to that event receive reminders from GReminders, it is pretty simple. 1) Connect your Google Calendar to GReminders, 2) Set up an event on that same Google calendar. That's it. GReminders does the rest. Now there are some advanced settings and tips, of course. For that I would refer you to their video walkthrough here: https://www.youtube.com/watch?v=nlNtSBFKm8w

Your Google calendar is synced with GReminders so within the settings of the app, you can create criteria for which events generate reminders, what they say, and how they are sent (email, text, etc). Once you set all of that up, you just let it work.