There are two ways to email a staff member regarding a shift.
The first opportunity is when creating a shift you can chose to notify staff members they have been scheduled for a shift.
If a shift already exists you can notify them in the same way whilst making editing the shift.
For an existing shift, should you simply want to send a reminder of the details you can do so by clicking on the share icon whilst viewing the details of the shift:
This will email or SMS the details through to the staff member(s) you chose.