Step 1: Login the site using phpmyadmin
Step 2: Select the Database
You can find you data base name, user name and password on database from configuration.php file of joomla.
Step 3: Select the Users table "jos_users", on left side of panel from the database.
Step 4: Select the Browse in middle window and edit the user name Administration, id e.g 62 by clicking the edit mark "pencil" in this case.
Step 5: In the password field, insert this value "226776f356d7ecf58b60bab12a05d38f" (without quotes), this is hashed value of joomla, new password of admin user. Be careful do not change field type.
Step 6: Press Go, make sure the save option is selected in the bottom of window.
Congratulation you new password joomla is set.
Do not forget to change the password of admin when you login.