pi

Open a terminal

sudo apt-get update

sudo apt-get upgrade

ifconfig

Note your wireless adapters…if any are installed

lsusb

Note the USB devices on the pi. You will not see the ALFA wifi device

Next type

sudo apt-get install realtek-rtl88xxau-dkms

Drivers will install, this may take a few minutes.

Once it is done type the following

lsusb

You will now see the Realtek Adapter

ifconfig

You will now see your ALFA wireless card