You will need to install and activate Cornerstone as well so that you will get all the options for X although Cornerstone should be automatically installed on your site if X is active so kindly try to check your plugins page and enable Cornerstone.
If the issue persists, try testing for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it's fixed, you'll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
In case you are still not getting the option, please provide us with the admin access to your site in a Secure Note: