Navigate to phpMyAdmin and select the database for the Joomla! site in the left-hand drop-down list box. This will show the database tables on the left side of the screen.
Find and click on the table with "_users" appended in the list of tables.
Click on the "Browse" button in the top toolbar. This will show all of the users that are set up for this site.
Find the user whose password you want to change and press the Edit icon for this row.
A form will display that allows you to edit the password field. Copy the value
login with admin password