There is not a way to edit the Registration Page to add text to the Field Labels.  You can edit the Section Headers, such as the Contact Information Label, but the individual field labels cannot be changed.  To edit the Section Headers:

1. Navigate to Fundraising > TeamRaiser
2. Click Edit next to the TeamRaiser in question
3. Go to step 13. Customize Pages
4. Click configure next to page you would like to edit