You do not need to do anything to make scrollable for panels. When your panels have long contents the scrollbar will show automatically.
I checked your site and see some errors. Maybe it causes the plugin is working wrong. Please re-check your site and fix the errors.
I also see your site is added many jquery library versions. It is not a good practice. You should consider to use only one jquery version for best performance and stability.
P.S: please do not show your purchase code on a public place. Just use "Add license" feature on this site to add your purchase code. I will remove the purchase code in this ticket (I saved your code for your account).