How to use qwt?

[ssaguiar]

Hi:

I wish to know how can I use the qwt in my app because I just don't get it. My app is working ok, but I need to plot a 2D grph in a QLabel container (or anything that is more apropriate to use with qwt).
I tried but can't find where to insert the code. The qwt is very poor in tutorials.
I wish to have in my app something like the QwtSpectrogram example.
Attached is my code.

Thanks for any help.