Unfortunately we cannot offer support services for other vendors products, outside of integration assistance for Genian NAC users.
I was able to find some resources from 4ipnet that should be helpful top you:
- Captive Portal config Video Demo: https://www.youtube.com/watch?v=lqfg_jCSMKU
- Official 4ipnet Technical Support: http://www.4ipnet.com/support/technical_support
We wish you well in configuring your network.