setting up a fortigate 110c to work with a zxr10 1822E

I have and internal network of 50 computers that I need to connect to the internet via a fortigate 110c firewall and a zte zxr10 1822E router. How do I connect the the firewall and the router ? Which should be connected to the internet vsat modem? Also how do I connect 2 zxr10 2952E switches to create a single collision domain?