Adding your own custom RTMP is very easy using XSplit Broadcaster. All you have to do is click on Broadcast >> Edit Channels >> Add >> Custom RTMP You will be shown with this interface.
Here's a quick video for it:
If you are using 3rd party streaming service, the service provider will typically have information on how to set up your broadcast using a predefined RTMP URL and stream name for channels assigned to you.
See it in action!