If the CMS you are using is listed in the following posting contact the CMS vendor as they provide the connector *http://forums.xmetal.com/index.php/topic,608.0.html
If you are using Documentum contact the XMetaL sales team and inquire about XMetaL Author Enterprise for Documentum Webtop
If you are using Sharepoint contact the XMetaL sales team and inquire about XMetaL Author Enterprise - SP Edition
If you want to build a connector to allow XMetaL Author Enterprise to interact with your own company's CMS (something not listed above) please contact the XMetaL sales team. An SDK is available to partners. Keep in mind that this is usually a significant undertaking that takes most partners between 3 to 6 man-months to code and test and can require ongoing development and testing if CMS functionality changes (the XMetaL connector APIs are generally guaranteed to remain stable). http://xmetal.com/content-about-contact-us/
* Connector is our term for the code added to XMetaL Author Enterprise that uses XMetaL's "connector SDK" to extend the relevant portions of XMetaL's UI so they can properly communicate with the CMS. Similar terms used for this are "bridge" and "integration".