How do I send reminders to people who signed up?

You do not need to. Everyone on a signup gets a reminder email the day before, at the hour set in Reminder the day before at. Change the hour under Edit details and spots and click Save changes. Families who add a mobile number and tick the text box also get a text. To send your own note, use Message the volunteers on the signup page. An email costs 1 credit and a text costs 3 credits per 160 characters.