Each Generic Content based module supports metafields. You should have declared a provider for your custom module and under metafileds section of the web.config file your metakeys. Make sure that you have setting and manager elements in your module manager class
/// Gets a settings element for our module (generic content implementation for news) within web.config.
, GenericContentElement> ContentSettings
/// Gets manager responsible for working with content.
If you have some specific problems with any implementation, let me know. Generally the products
module shows almost the whole basic implementation of an Generic Content based module.
the Telerik team