Attached you can find an example of how to use ST_GEOMETRY with Telerik OpenAccess ORM. This sample uses the Fluent API to set up the respective model and is using a custom converter to implement the logic for ST_GEOMETRY. You can also find information about how to work with converters in this and that link.
I hope this information is helpful for you.
Do come back in case you need further assistance.
the Telerik team