I've been searching this but I can't figure out how I update the phpMyAdmin folder in the opt/lampp folder. When I try to delete the content of the folder it says that I don't have permission to change it.
The phpMyAdmin included with XAMPP is integrated in to the whole package, so my preferred method is actually to install your own phpMyAdmin to another directory name inside the web root, that way you have complete control over it and don't affect anything within XAMPP.
However, another method is to simply replace the existing phpMyAdmin directory that's included with XAMPP. That has the dual advantages of integrating nicely to any existing links from within the XAMPP system and also not leaving you with two phpMyAdmin installations, but I have no idea what customizations the XAMPP folks do to phpMyAdmin when they include it and this might upset some fragile piece, so definitely make a backup of the old folder first.
For help on your permissions problem, you should post a new question with relevant details (the exact error message, permissions of the folder, your operating system, etc).