You can customize your email templates the same way you can customise the other templates - from the Templates section.
What emails can I customize?
Customer New Reservation Confirmation Email
Sent to customers after they submit a new reservation request.
Store Manager New Reservation Notification Email
Sent to the location's email (usually the store manager) with information about the customer that is coming to pick up the item.
If you need to customize the Store Manager New Reservation Notification Email then please let our support team know and we'll help.