This step tells Let's Encrypt that you're serving
                                        the correct data for this challenge on your server.
                                        When Let's Encrypt receives this submission, they
                                        will make a request to your server to verify you are
                                        serving the data correctly.
                                        
                                        How to generate this signature:
                                        
                                            - 
                                                Copy and paste the command below into your terminal (if your
                                                account private key isn't at "./account.key", change "./account.key"
                                                in the command to wherever it exists).
                                            
 
                                            - 
                                                Copy and paste the hex encoded signature output from the command
                                                into the text field below that command.