$ sudo apt-get update
$ sudo apt-get install glx-alternative-fglrx 

glx-alternative-fglrx is installed in your system.

Make ensure the glx-alternative-fglrx package were installed using the commands given below,

$ sudo dpkg-query -l | grep glx-alternative-fglrx *

You will get with glx-alternative-fglrx package name, version, architecture and description in a table

glx-alternative-fglrx package basic information: