as far as I could find out, you only can activate 2step auth for any of the 3 options and it's a one way street.
once you enable it for any of the options, it stays on and can not be changed later.
the good news is, all 3 options when activated, return the same code so it's enough to write it down once.
if you missed three chances to write down a code can't help you.
if you can't do anything now means you already clicked on all 3 buttons that activate 2step auth for withdrawal, transfer and password change and you're done. if you did not have 2step auth activated prior to that step, no idea how to help you now.
if you need a new account, just create a new one (with a different email, though) and use the new one.
deleting an account is something only nefario can help you with
Setting up the account was a mess. Everything I did led to a "Internal Service Error" and after twenty tries with different emails, usernames, and two step auth settings, I finally got in. However, I don't know which email it is using or which two step auth choices I selected, and the password is temporary and very weak. Also, nothing shows up under settings, so I can't view/change email, view which two step auth settings are selected, or change password. The settings page shows absolutely nothing. I'd rather have the account deleted and try registering again. However, Nefario is not responding to days old PMs, even though it shows him as "online" many times since I've sent the PMs. This has been a very frustrating start to GLBSE.