Question #1
How do I use my Time Capsule as a router?
Connect an Ethernet cable from one of the LAN <-> ports on your modem/router to the WAN port (circle of dots icon) on the Time Capsule.
Open AirPort Utility and click Continue to follow the guided setup to configure the Time Capsule to "create a wireless network". Select the "Bridge Mode" option when it appears during the setup. (AirPort Utility will normally do this for you)
Question #2
If I do this will I still be able to wirelessly back up to my Time Capsule?
Yes
Question #3
How do I turn off (wireless) or the router function of my modem/ router?
We prefer not to guess at things, but since we do not know the make and model number of your modem/router, and this is an Apple support area, we have little choice.
In general, you would enter the default IP address of the device into your browser to bring up the configuration pages (check your documentatio on the modem/router for this information, or it may be on the back or bottom of the device. An example of a default IP address is something like 192.168.1.254
There will be a wireless settings page that will allow you turn off the wireless function of the device.
If you acquired the modem/router from your service provider, they should be able to tell you how to do this as well, or if you check the manufacturer's website, they will likely have a support area for questions like this.
Question #4
I then want to connect all my wireless devices to my Time Capsule making that
the main WIFi in my house.
You will need to log on to the Time Capsule wireless network from each device and enter the password to connect. Most computers will "remember" the setting so that you do not have to enter the password each time that you connect.
