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