1. Visit the URL http://<your_domain>:8880 and login
2. Go to the files from the top menu section or file manager section for the domain you want to access
3. Click on the collapsed menu on the right of the directories or files you want to change permissions, then Click on the change permissions link.
4. A popup will open, from where you can update the permissions(rwx) for the owner, group and others as per your requirement and click ok