Step 1: Login to your cPanel.
Step 2: Select the PhpMyAdmin under Database option.
Step 3: Select the database that you have currently uploaded along with website.
Step 4: Click mg_adminuser on the list.
Step 5: Under the username, you will see the registered users.
Step 6: Select the username that you wish to reset the login details.
Step 7: Under the password column, clear the value and enter the new login details.
Step 8: Finally click Go option.