How do I change my font from free download to paid download?

http://www.dafont.com/member_account.php
- click on "update" next to your font name
- chose license type

(that's all you can do. It won't prevent people from downloading it for free if that's what you wanted to do)

You might want to consider how Brittney Murphy does it. She has all her fonts available here at Dafont as Free for personal use (http://www.dafont.com/brittney-murphy.d2425) and the same fonts are available at CreativeMarket for $5 each (https://creativemarket.com/brittneymurphy)

thanks daaams and toto@22