Your network device configuration tool probably has a gateway entry field.
You can manually add a route using the "route" or the "ip" command.
For example, if the router at 188.8.131.52 is for the 10.0.0.0/8 network, and the router at 184.108.40.206 is the default gateway, you could use:
route add -net 10.0.0.0 netmask 255.0.0.0 gw 220.127.116.11 dev eth0
route add default gw 18.104.22.168 dev eth0
Also look at the man page for the "routes" configuration file. You can enter routes there.
Indicating which distribution you are using might be helpful.