Skip the rest of the inputs and click the button at the bottom left of the page that says “Sign in Transaction Signer”. On the next page, scroll to the bottom and either paste in the Distribution Account secret key in the text area next to “Add Signer” or sign in with your Ledger Wallet. If you are using your Ledger Wallet, you will need to confirm the transaction on your hardware device. After signing the transaction, scroll down and click the 'Submit to Post Transaction endpoint'. After submitting your operation to the transaction endpoint, you will be taken to a new page that summarizes your transaction. Press the "Submit" button.