DT Register is not setup for you to easily be able to add your own gateways, although it IS possible. It's more complex than just updating one or two files though. We do not support your own customizations, but if you'd like to pay us to do the customization for you, let us know and we can discuss that.
Nathan is no longer affiliated with DTH since the recent acquisition. You can connect with him and get any type of Joomla website help at
www.JoomlaEmployee.com
.