Find the below article helpful on how to send email to a particular section.

1. Click on SMS Manager on the left side
2. Select Send SMS to the function display under SMS Manager 
3. Click Send Bulk Email
4.  Click on the All section to select a class from the section 
5. Type the message that you want to send inside the text box area
6. Click on Send Emails
   Lastly, click OK to confirm your action.