I haven't tried the web-site.

Unless you manage to install rtmpsuck, you may have problems with rtmpdump. You need to find a stream URL first. Then use it in rtmpdump. Don't forget to use the live parameter, since you want to download live private sessions.

If it is too difficult for you to use, there is a huge community of rtmpdump fans here and you should be able to get help from them. But you need to learn and post more details about your problem.

You can also try the following software for Windows:

If you need an easy to use software, then you can use Jaksta if the web-site uses RTMP streams. The program allows to capture packets from flash player, so the content providers will never notice you recording.

If the web-site uses secure RTMPE protocol, you can try to use RTMPE recorders.