URGENT - Cross-tool gcc/cpp/g++ Installation Problem

Hello There,

I need to install  cross-tools for building Qt C++ applications.  The *host*
is a Virtual Machine (VM) Debian 8 (Jessie?), and the *target* is
BeagleBone Black (BBB)  with Debian Jessie (8) and a touch screen.

I have tried installing various cross-tool packages on my VM using apt-get
but in all cases it fails saying 'E: Unable to locate package [package
name]'.  For example:

prompt>  apt-get install arm-linux-gnueabihf-gcc

                        Reading package list... Done
                        Building dependency tree
                        Reading state information... Done
                        E:  Unable to locate package arm-linux-gnueabihf-gcc



Will be thankful for your help / advice soon!
Hear from you soon.


Kind Regards,