I have lost my administration password

From Documentation

The password is stored in the user table and it is encrypted. You can get a new password by visiting http://yoursite.com/userforgot.php and having a new one resent.

Once you receive the new password try logging in to the administration. If you are unable to login you will need to login to your database control panel such as phpMyAdmin then go the user table and find your username. Next modify it and change the level to 1.