Basic Configuration for Fortigate FG-30E

Hi,

I am new to Fortinet. Would like someone to help me to sort out this basic configuration because I have tried so many times but failed to connect my internet ISP to my office networking. I have bought a Fortigate FG-30E-BDL and try to connect it with my Router Modem (gateway: 192.168.1.1) to my local networking (IP Range 192.168.1.10 - 192.168.1.100). I have 18 computer connected in my local networking. I would like to know how I can connect my internet router to my local netwoking with basic firewall. I would appreciate if someone can guide me.