Head over to your profile, click on My Logins & click on Add More logins.
Now, at the login page, login with another openID provider, or create a Stack Exchange account. You'll be able to login to your account using the selected openID provider or using Stack Exchange account
Create an OpenID at https://openid.stackexchange.com/
Go to you profile page (https://webapps.stackexchange.com/users/20021/loldop)
Click on the "my logins" link.
Click on the "add more logins..." link:
Select "log in with Stack Exchange" and enter the details created at step 1.
Optionally remove the existing login by ...