(18) How do I regain my SE account?
If you participated on the Theoretical Physics Stack Exchange, or the Physics Stack Exchange, then your posts may already have been imported, so you may already have an account on Physics Overflow. Please search for your account to check if this is the case.
Enter your username, and press "Search".
If you are lead to your profile, your account exists. Then you can regain access to your imported account. To do so, click on "Regain SE account" in the sidebar sidebox. Enter the email, username, and password that you used on TheoreticalPhysics.SE or Physics.SE.
Then press "Register". You will then be logged in to your account, where you are recommended to change your password. If your SE account is deleted, you can register as a new user and ask for your imported posts to be assigned to your account as described in the sidebar sidebox. If you accidentally register as a new user, even though you have posts which were imported, you can ask for your accounts to be merged as described in the sidebar sidebox. If you don't remember your account particulars, you can ask an administrator to send them to you as described in the regain account page.
If you never had an SE account, or never had graduate-level posts on SE, just register as a new user.