Extending range of Airport Extreme (old round model)

Hi,

I have 2 airport extreme base stations (old model - round ones). I have set one as a Main on WDS network and the other as a Remote. However, it does not seem to be working. I have followed the instructions given here: http://support.apple.com/kb/HT4262

But it is not working.

Now, Airport Utility (5.6.1 is the only one that works with these stations) does not even display the second base station.

Is there a step by step document that explains how to set such a network up? Or could someone take me step by step through the process?

Thank you very much for your help.