Ideally, connect the device 1-2 days before the expected stressful event. Insert the plug into a normal socket in your cat's favourite room. Leave the diffuser plugged in day and night to achieve the best calming effect.
The packaging of some Feliway Help diffusers indicates that the plug should be inserted into the socket at an angle; this refers to European sockets. In a standard British socket, the diffuser stands upright and cannot be rotated.