Using 2nd wifi router as Guest Wifi

If you just want a separate LAN (accessible by "guests" with wired or wifi) then all you need is to connect the ASUS as you did to its WAN port and make sure that is running its own DHCP server and to avoid confusing yourself set a different range of internal IP addresses for this LAN (e.g. 192.168.8.1-192.16.8.50).  Your ASUS will pick up its own IP address from the DHCP server in the T3200 (and this is the one you will use to get to the ASUS management screen).  Effectively all you are doing it running 2 separate LAN's within your space - one run from the Router part of the T3200 and one run from the ASUS router.  The T3200 still uses its modem part to provide connection to the WAN and its wifi to allow connection to its router part.  If you need incoming port connections to the WAN for the guest network then they will need to be configured on both routers.    If you had got the Telus fiber then you would not have needed getting the T3200 at all.  You would have asked for an ONT instead (converts glass to ethernet) and hooked it up with a >cat5e Ethernet cable directly to the WAN port on your ASUS.  But then you take on the responsibility for getting your LAN working - Telus are only providing the "pipe to the internet" - the WAN connection to your LAN.