Sorry for the delay in replying but I needed some zzzz.
The MySQL password is the same for phpMyAdmin - make sure you type it in exactly as you created it.
Paste the error message you receive when trying to login to phpMyAdmin using root as username and the MySQL password you set in the security page.
Also try and access phpMyAdmin without a password using root as the username and again let me know the error message if you are not allowed in.
When you go to http://localhost
are you asked for a password and if so when you enter the password does it let you see the XAMPP Welcome page?