If you started the application and used a backup to import all the data from a prior version, then you will need to use the username and password you have used before. If the application was freshly installed, you will be taken to a page where the admin username will be created along with its details regarding address, password, reset features, etc. If you don't know the password, back up your data using the Export function and backup menus, then perform a new installation of the product.
