You can’t.
People here are going to tell you that there is, they are going to make a variety of suggestion for work arounds.
And I tell you don’t bother wasting hours like I did downloading, setting up and trying them with Blizzard’s system after the locked bag slots appeared because they will not work because the following, and only the following, is acceptable:
And yes, it is very frustrating. I cared enough about account security to buy the physical authenticator back in the day so if Blizzard had any other option than the above I would take it. They don’t. They expect you, on top of paying them, to also pay for a monthly contract with a cell phone provider for security.
It is arrogant and presumptuous.