How to Setup FortiGate Firewall to Access the Internet

Step 1: Login to the FortiGate’s web-based manager.



Step 2: Go to System –> Network –> Interfaces to Configure the WAN interfaces.
 


Step 3: Configure the internal interface, In this case DHCP is enabled.



Step 4: In the MAC Address Access Control List, assign the mac address and IP address of the administrator PC.

Step 5: Configure default route at Router –> Static –> Static Routes, Set the Destination IP/Mask to 0.0.0.0/0.0.0.0,
the Device to the Internet-facing interface, and the Gateway to the gateway (or default route)
provided by your ISP or to the next hop router, depending on your network requirements.
 

Step 6: Configure Policies, in General Policy Only HTTP, HTTPS, DNS services are allowed.

Step 6.1: Make sure to Enable NAT and session logging as well.

Step 7: in Administrator PC policy, firstly you have to create a new address for admin PC at Firewall
Objects –> Address appropriate subnet number and the interface is configured

Step 7.1: Then create the policy for admin PC. All the services are allowed in this case.

Step 8: Test the policy configuration by accessing internet using the admin PC and another PC in the network.
Monitor the counter changes in policies.

Credit : https://techencyclopedia.wordpress.com/2017/08/13/how-to-setup-fortigate-firewall-to-access-the-internet/