Log into your cPanel account and click on phpMyAdmin
Open the database that your OpenCart store uses
Find the "user" table
Edit the user with the username "admin" and change the password field to 5f4dcc3b5aa765d61d8327deb882cf99. This string or hash changes the password to "password"
(without the quotes)
Now, attempt to log into the OpenCart admin with your new password