Please first read https://www.akeebabackup.com/documentation/troubleshooter/atadminpw.html under "I enabled this feature and now the front-end of my site asks me for a username and password". If you have further questions please feel free to ask us for further assistance.
Nicholas K. Dionysopoulos
Lead Developer and Director
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!