ITS provides support for using and resolving issues with OpenStack on Nebula but does not act as system administrators for each of the instances that the users create on the system. Some issues might be covered in this FAQ, you might get help on the chat group, Google is your friend.
How can I restore a filesystem that has been set to read-only?
A description of how to recover when OpenStack marks one of your files read-only is here.
How do I create an instance?
There are a lot of options you can select when you create an instance but at its most basic you select the amount of resources your instance will use by selecting a flavor and you select where your instance will get the operating system that it will run from. You can choose to have your instance boot from an existing image, a snapshot taken from another instance or from a bootable volume. The Getting Started document walks you through the steps to create a basic instance that boots from an image.