I have a secondary router that's out of use now, I think it's a Telkom Netgear N300
Just verify if your router has a WAN port. Found this manual check around page 11
http://www.downloads.netgear.com/files/GDC/DGN2200V4/DGN2200v4_UM_26Mar13.pdf .
-So you would just need to have a cable run from the designated WAN port on the ADSL router to any LAN port on the Huawei.
-Make sure your ADSL router's LAN network is in a different network from the B593's . If the B593 is using 192.168.1.1 then on the ADSL router use something like 10.0.0.1 or 192.168.2.1 for LAN
-Set internet connection type to WAN on the ADSL router
-Give the ADSL router's designated
WAN interface a static IP in the same subnet as your B593 ( something like 192.168.1.2 255.255.255.0)
-On the ADSL router set your DHCP options to include Unotelly's DNS servers when clients request IP configurations
-Connect your clients to the ADSL router's wifi / Ethernet and they will get UnoDNS settings and traffic will be routed through to the Huawei
-Optional , you can completely turn off wifi on the B593 to avoid clients connecting to the wrong Access Point which doesn't have Uno's configs
Edit: Came across another manual -->
http://www.downloads.netgear.com/files/GDC/DGN2200/DGN2200_UM_3Feb11.pdf check page 10, looks like there are some versions which don't support WAN internet. So just verify what you have