1. Go to evenium.com
  2. Click on My Events
  3. Click the name of the event under the I Organize section
  4. Click on Configuration on the purple bar
  5. Click Invitations & Emails
  6. Click Edit invitations & emails
  7. On the next page, you'll see under the Message section on the top left a New message link. 
  8. Click on it and create your own custom template and send it to your participants!