This is a bit challenging.
I'm not a NuPoint tech but I can give you a high level overview of what to do.
1 - create a new port group with the port you want to dedicate to the RAD.
2 - set that port to answer with either a greeting only mail box or a AA box that plays the greeting then hangs up.
3 - record the greeting, dial the port and put a stop watch to it, timing how much time is used from the time the port answers until the end of the message. This is your "message timer" value.
4 - in the 3300 create a new COS. Enable the RAD option. Set your "off hook timer" to it's maximum. Set your message timer to match what the message length you timed in step 3.
5 - assign the COS to the Nupoint port.
6 - assign the New Rad port to your ACD path.
7 - test by dialing the ACD path and letting the RAD answer - note: you cannot test by dialing the port directly.
To me, using a NuPoint port as a RAD is a waste of some valuable real estate. Better to use the embedded. It's easier and less expensive.
Ralph