Permission Issue on AWS EC2 instance

Hello, I am facing permission denied issue while creating new file or folder on cpanel file manager also I am unable to edit, delete folder/files on cpanel file manager...In addition to that issue, I am unable to open phpmyadmin,it shows "Error during session start; please check your PHP and/or web server log file and configure your PHP installation properly. Also, ensure that cookies are enabled in your browser." I have tried the google search, StackOverflow, AWS forum but unable to solve this issue.. I also attached screenshot of error. Kindly Help me.