I am currently taking the course Admin Trail Begginer: Getting Started With the Platform, when I proceed to sign up for a DE account I get the following message: "Sorry, we can't enroll you in a Salesforce Developer Edition account because the email address you entered is already in use. To sign up with a different email address, go to https://developer.salesforce.com/form/signup/freetrial.jsp ."

Does this mean I already have a Development Edition Account? If so where would I access it? 
Or should/can I sign up with any email adress fir a DE?