There seems to be some confusion here over two very different devices. The OP is talking about a WIFI antenna signal BOOSTER, not a router that gets whatever it gets & rebroadcasts the signal, a wireless router.
If the antenna on that device gets a lousy signal, it can't improve it.
The directional antenna focuses on the CG WIFI router & boosts that signal by wire into your laptop, or whatever it is plugged into. It works like your directional over the air TV antenna or your satelite dish. You need to know where the source of the WIFI signal is & point the little dish in that direction.
Omnidirectional external WIFI antennas work too, better than the laptop internal antenna, but nowhere near as good as a external, not necessarily outside, directional antenna.