copy and paste the below
curl -L https://raw.github.com/txt3rob/Aircrack-NG_RaspberryPI/master/install.sh | bash
follow the on screen instructions and your raspberry pi be able to do packet injection.
If you wish to donate to me my email address is [email protected]
Alfa Network AWUS036NHA IEEE 802.11b/g/n wireless USB adapter http://amzn.to/2xyP7Py