In order to set up 2FA in MirageID for sellercentral.amazon.com follow these steps:
Go to your login settings:
Under 2-Step Verification select "Manage":
Then select "Add New App":
On the resulting page, click on "Can't scan the barcode?":
Copy the Secret Key from the popup:
Click on the "Key" icon on the top of the MirageID Browser window:
Click on the "down arrow" to the right of the password manager entry this token is for:
Click on "Set up 2Fa":
Paste in the Secret Key that you copied previously and click Save:
Then copy the resulting 2FA Token:
And paste it into the field, click "Verify OTP and continue"
That's it! You are all set to use the 2FA support in MirageID.