You can customize the welcome e-mail that is send to trainees.
There are two e-mails. One when a new account is made and one with the invitation for the program.
Go to Account and click on the tab Emails
Here you can customize the email to new users.
When you enroll a trainee in a program, an invitation email is send automatically. You can customize this email in the following way:
In the program for which you want to change the invitation go to the Settings tab.
Scroll all the way down to the bottom. Here you can customize the invitation email.