Allowing an IP address to access a Facebook

Hi all, I need help since I'm new to Fortigate. My company utilized FortiGate 300D, (5.6.0) we also rely on it on web filtering.(configured by contractor previously) Normal practice our staffs able to access internet, but not allowed to access Social Network webs (e.g Facebook, IG,twitter...etc), however one particular staff is assigned to update,monitor and maintain our company's Facebook page on daily basis. How to allow his particular IP (machine) to be able to access Facebook.

FYI : I've tried to look for exceptional option on web filtering but didn't find it.

Really need your help on this matter. A million thanks in advance

Regards Azmi