unable compiling program using qt 5.6

Hello,

I use Ubuntu LTS 14.04 and need to install a program which requires qt >= 5.4.

I installed qt 5.6 using the online installation script http://www.qt.io/download-open-source/ - no problem at all.

Now qt 5.6 is installed under /opt/Qt, the /bin and /lib directories are /opt/Qt/5.6/gcc_64/bin and /opt/Qt/5.6/gcc_64/lib.

I have also other versions of qt installed in the ubuntu default locations.

I tried a number of path settings in .bacsrc, .profile..., /etc, ... which are described online but nothing worked, qmake doesn't recognise qt 5.6.

How can I set the path to qt 5.6?

E.