A quick look at their site really shows a lack of documentation so maybe it's the old 2.4GHz video links and not 2.4GHz WiFi links which can't be extended.
I'd look into a refund so you can look at Ethernet connected cameras with POE that will give you a lot more options.
Parting thought. I do encounter folk that insist on the DVR being in a basement (where WiFi goes to die) and have found moving the DVR closer to the cameras solved it but you can guess that clients at times want what they want in spite of the tech issues. You can't help them.
I bought a floureon wireless nvr kit from ebay. The cameras are fine, as long as they are within range of the nvr. My problem is that their wifi range is not all that large.
I looked into extending the range of their wifi but connecting their wifi signal to an extender doesn't seem possible as their signal (2.4) seems to be different. The other problem is that floureon is not real big on either support or a decent manual.
Anyway, I want to place one camera where I also have a connection to my main router and was wondering if there was a way to connect through this router connection. The nvr is already connected to my router and the internet and I have 2 wireless cameras hooked up to that nvr. Now I want to add another and thought a direct router connection might be the ticket.