configuring OSPF between Fortigate unit and Cisco Router

hello fellas,

i have new deployment for fortigate in a network environment that contains Cisco Router in a side and the new fortigate in other side. and i need to configure a dynamic routing protocol which is OSPF and it seems a little confusing.

i am preparing the network topology to support my topic.

Site A:  "Fortigate 300C"

Interface 1 -->  ISP 1    -->   dynamic route "OSPF"

Interface 2 -->  ISP 2    -->   static route with higher metric

Interface 3 -->  LAN

Site B:  "Cisco Router"

Interface 1 -->  ISP 1    -->   dynamic route "OSPF"

Interface 2 -->  ISP 2    -->   static route with higher metric

Interface 3 -->  LAN

note, connection between Site A & B is initiated through both ISPs.

i have gone through OSPF configuration but seems not clear to me.

appreciate to hear from you..