If you want to use your sphere login to register for a thon event or any event, you must use the 'Autofill' option.

1. Here is the text that you will see upon registering,
If you have participated in any Friends Asking Friends event in the past, click here to Autofill this form.
2. Click "click here" link
3. Type your sphere username and password to log in
4. System will auto populate some of the fields within the registration form
5. Continue filling out the registration form 
5. Click Submit