I can't seem to set defaults for firstname lastname email

How can I set defaults in forms for firstname lastename email address?

Do you mean like hint example? If yes, click on it's gear icon, then on "Edit properties":

Then click on ADVANCED, and type the example in the place holder box:

Result:

If what you want is to prepopulate users information, here is how: http://apps.jotform.com/app/field_prepopulator 

If this is not what you mean, please provide more details of what you want to accomplish, we will be glad to assist you.