Explara provides certain system-defined email templates which are editable to a larger extent. In order to find the list of email templates, please click the manage icon of the event. You will see a couple of menus on the left side, you see the main menu named "Email Templates". Click this one and you will all the system-defined email templates. Select the one you want to edit.
You will find editable blocks and edit/delete icons. You can use these to make changes to the template. Also, you can add additional blocks from the left side "Element Block". You can make other changes by using the "Settings" option that gives a broader handle to make changes to the template.