Script to install the ASUS USB-AC56 / Dual-band Wireless-AC1300 USB wifi Adapter
1] Make sure your raspian is up-to-date, apt-get update; apt-get upgrade; 2] run this install.sh script 3] reboot your pi
or just go and use this
https://www.raspberrypi.org/forums/viewtopic.php?t=178405#p1136676