Enter inside the group that you want to contact, press the 3 vertical dots menu and select Contact… option.
You can contact individually or massively with students or with their responsible persons. In the following example, we have chosen to do it massively to the students. After selecting the option, the list of students of the group will appear to choose the ones you want to contact.
Once selected, press the Send email option. It will open the mail program you have set on your computer or device in order to write and send it.
NOTA: remember that for use this function you must have previously configured your email in a program to read and send emails (Microsoft Outlook, Mozilla Thunderbird, Mailbox, Mail ...) and also have introduced all students or responsibles emails in the student record (See tutorial: Fill out student personal details).