Your router will no longer be connected like this. It's going to only be used as a Wireless Access Point, and will connect to your primary switch to a LAN port on the router, not the WAN. I don't know for sure what IP address scheme you are wanting to use, but I'll give an example below and you can set the IP address information then to what you want.
SONICWALL TZ 105
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Interface X0:
Zone - LAN
IP Address: Static 192.168.5.1
Subnet Mask: 255.255.255.0
DHCP Server: 192.168.5.50 - 100
Primary DNS Server: 192.168.5.253 (the IP address of your Domain Controller/DNS server)
Secondary DNS Server: 8.8.8.8 (or the IP address of your ISP's DNS server)
Interface X1:
Zone - WAN
IP Address - DHCP (will be assigned an IP address by the modem. If you don't want this, and know the IP address range your modem is in, assign a static IP address in that range.)
Interface X2, X3, X4:
Portshield Mode to LAN Zone (this makes them basically switch ports on the same LAN network as X0 interface.)
Once these settings are done be sure to do a restart on the firewall so that the running configuration is completely saved. Now to connect the other devices. You will plug Eth1 port of your primary switch into the X0, X2, X3, or X4 port on the Sonicwall. They all go to the same network, so any one of those interfaces should be fine for now. Connect up your wired connections to your primary switch, and you will also plug in your wireless router to the switch. Connect the switch to LAN port 1 on your wireless router, not the WAN port. Your router will no longer be doing any routing, and will act basically like a wireless antenna for your existing network which is now managed and routed by the Sonicwall. You will want to configure the IP address settings of your wireless router by logging into it's configuration page. You will probably need to first access to the IP address of what was previously your default gateway (often times 192.168.1.1) to get into the original configuration of the wireless router. From there you can change the IP address information and other necessary settings.
WIRELESS ROUTER
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IP Address: 192.168.5.2
Subnet Mask: 255.255.255.0
Default Gateway: 192.168.5.1
DHCP Server: DISABLED (your Sonicwall currently is running DHCP, not the wireless router.)
Again, be sure you save and reboot your wireless router to ensure that you have saved the settings. You should now be able to connect devices onto your wireless network. If you are using Static IP addresses on your computers, set them up in the 192.168.5.0 network, such as the example below:
IP address: 192.168.5.10
Subnet Mask: 255.255.255.0
Default Gateway: 192.168.5.1
Primary DNS Server: 192.168.5.253
Secondary DNS Server: 8.8.8.8
If you are using DHCP on your computers, then open up the Command Line utility (from the Start window start typing CMD and hit Enter.) Type in the following commands to release any previous IP address settings and request new IP address information from the DHCP server at the Sonicwall:
ipconfig /release
ipconfig /renew
Make sure that the IP address your computer picks up is in the 192.168.5.0 network with the other correct information. Once this is done, it's time to test and troubleshoot settings. Let me know when you get to this point and I can help out with determining what you might be running into for problems getting network connectivity if you do.