Declare Fear of Missing Out as an attacker, choosing to exert it as it attacks and triggering its ability, causing you to untap all other creatures you control and to get an additional combat phase after this one.
Deal combat damage to an opponent using Fear of Missing Out, triggering Impostor Syndrome, creating a token copy of Fear of Missing Out that isn't legendary.
During your next combat phase, declare Fear of Missing Out and the Fear of Missing Out token as attackers, choosing to exert the Fear of Missing Out token as it attacks.
The Fear of Missing Out token triggers, causing you to untap all other creatures you control and to get an additional combat phase after this one.