Which versions of AOS and CP are you running?
Are you trying to:
- Redirect to a specific site after login or
- Redirect to the original web-page you tried to navigate to before Captive Portal?
For nr 1 just input that in the Welcome Page on the CP Profile. In my experience doing that on the ClearPass Guest side doesn't do anything, but it might be working on latest version...
For nr 2 there isn't a straight forward way of doing that - unless you implement a CoA based solution. Then I'm pretty sure you can send the original URL back as a redirect parameter.
The guide you are using does have the key points to creating a welcome page on ClearPass that has the URL stored for the original URL, but it will require a click by the user.