Following is an example of Fortigate static NAT configuration, to statically translate the internal IP address 10.1.1.10 to 184.108.40.206
config firewall vip
set extip 220.127.116.11
set extintf "port1"
set mappedip 10.1.1.10
Following the VIP configuration, be sure to configure the policies to allow flow of traffic.
The policy that allows traffic coming from outside (Internet) should reference the VIP IP.
The policy that allows traffic from inside (Trusted or DMZ zone) should reference the original IP.