On this page you can do authorization in manual mode, without the convenience of the SEP-07 magic. For this, you will need a simple Soviet secret key from your account. And even more precisely — a legitimate signature of a transaction from your account. Even for users of multisig.
Below in the field, enter the Stellar address, click «Get transaction». Take this transaction, and, for example, in the Stellar laboratory, add the necessary signatures. After that, insert the result in the field below, and click «Authorize».
Under which account do you want to authorize? You will need to correctly sign the transaction for it.