Getting started with Drupal 7 administration

At the end of the installation process, the person who performed the installation is automatically logged into the site with the administrator account. You may see the administrator account referred to as User 1. This administrative account is automatically given all privileges for managing content and administering the site. The best practice is to only give a developer or the highest level of site admin access to this account. You can always grant users permissions by assigning them to certain roles, so there is no reason to share this account.
Where to start