If you'd like to send out manual reminder emails to a particular class in ASAP without configuring the option to have these go out automatically here is how you can do so:
1. go to Configure>Manage Emails and then select recipients by class 
2. complete all the forms for time period, location, group, and course and click "Add Students" button
3. proceed to next step compose and select "Create New" template from the dropdown menu
then fill out the text box and save (this will be saved for future use as a new template)
4. proceed to preview and send