Login into your Dev Edition -> Click on “Help” at the Top -> Click on “My Cases” -> Click On “Log A Case” -> Select the Case Reason as “Feature Activation Request” -> Select “Feature Activation” in “General Activation Area” and ask for the Person Account Enablement.
Make sure you meet the following prerequisites. …
From Setup, enter Account Settings in the Quick Find box, and then select Allow Customer Support to enable Person Accounts.