Hi,

Thank you for your message.

Ian is correct, Unless you want to develop a custom form control for this purpose, I would recommend using the Text Attribute type together with Media selection Form control.

You will enable this by selecting the Text attribude type and then seleting the Media selection form control underneath. You can find this settings in Development -> Custom tables -> Fields

If you decide that this functionality does not suit your needs, you can develop your own custom Form control as described devnet.kentico.com/docs/devguide/developing_form_controls.htm.