You will need to log into cPanel with your supplied username and password. Normally this URL is:
1) Select the Username field and enter your username
2) Next select the Password field and enter your password
3) Select the phpMyAdmin icon in the Databases section
4) In phpMyAdmin select the database used by your web site by clicking it
Scroll down to the jos_users table
5) Select the jos_users table by clicking on it
6) Now click on the Edit link for the user we want to reset the password for
7) Select the password field, deleting the existing value and replacing it with a new password
8) Next select the Function dropdown next to Password and select MD5
9) Scroll down and click the Go button
10) Now in your browser, open your Joomla admin and enter your username
11) Next enter the new password that you created in phpMyAdmin
12) Now click the Log in button
13) After logging in select the User Manager icon.
14) Click the name of the account you just reset the password for
Here you can change the password and Save the record to update linked tables properly
15) Reenter your password in the Confirm Password field
16) Click the Save & Close button
You now know how to reset your Joomla admin password using phpMyAdmin