So I've been having a lot of trouble getting it all to work with MSVC 64 compiler, and decided to put these simple steps which could have save me few hours if I knew it before.

My goal was to be able to plot, I am not interested in neither knobs/sliders nor the QtCreator integration, as a result this manual won't cover it. Just pure plotting capabilities and nothing else. Also, I wanted it to work with MSVC 64, because I build my Qt 64-bit applications with that compiler.

1) Make sure you have Qt installed with MSVC 2015 64-bit compiler

2) Go ahead download and install Microsoft Visual Studio Community 2015 to the default path

3) download the Qwt source zip file, and extract it to: C:\Qwt-6.1.3

4) Edit the qwtconfig.pri inside the C:\Qwt-6.1.3 folder, specifically, make sure that QWT_INSTALL_PREFIX is loaded in such a way that it points to C:\Qwt-6.1.3 and also comment out the following lines:
QWT_CONFIG += QwtWidgets
QWT_CONFIG += QwtDesigner

5) Next, open the command shell of Qt from the start Menu, Windows START MENU->Qt->5.7->MSVC 2015 (64-bit)->Qt 5.7 64-bit for Desktop (MSVC 2015), you will see the following message:
Setting up environment for Qt usage...
Remember to call vcvarsall.bat to complete environment setup!
6) Now, do the following command: C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC and that is the directory where you installed your MSVC Community 2015

7) Run this command: vcvarsall.bat amd64

8) Now go to Qwt folder: C:\Qwt-6.1.3

9) Run this: qmake qwt.pro

10) now run this: nmake

11) finally run this: nmake install

12) Create some simple gui application in QtCreator, so that it only has a main.cpp file, and enter this code (taken from here):
Qt Code: 
  1. #include <qapplication.h>
  2. #include <qwt_plot.h>
  3. #include <qwt_plot_curve.h>
  4. #include <qwt_plot_grid.h>
  5. #include <qwt_symbol.h>
  6. #include <qwt_legend.h>
  7.  
  8. int main( int argc, char **argv )
  9. {
  10.     QApplication a( argc, argv );
  11.  
  12.     QwtPlot plot;
  13.     plot.setTitle( "Plot Demo" );
  14.     plot.setCanvasBackground( Qt::white );
  15.     plot.setAxisScale( QwtPlot::yLeft, 0.0, 10.0 );
  16.     plot.insertLegend( new QwtLegend() );
  17.  
  18.     QwtPlotGrid *grid = new QwtPlotGrid();
  19.     grid->attach( &plot );
  20.  
  21.     QwtPlotCurve *curve = new QwtPlotCurve();
  22.     curve->setTitle( "Some Points" );
  23.     curve->setPen( Qt::blue, 4 ),
  24.     curve->setRenderHint( QwtPlotItem::RenderAntialiased, true );
  25.  
  26.     QwtSymbol *symbol = new QwtSymbol( QwtSymbol::Ellipse,
  27.         QBrush( Qt::yellow ), QPen( Qt::red, 2 ), QSize( 8, 8 ) );
  28.     curve->setSymbol( symbol );
  29.  
  30.     QPolygonF points;
  31.     points << QPointF( 0.0, 4.4 ) << QPointF( 1.0, 3.0 )
  32.         << QPointF( 2.0, 4.5 ) << QPointF( 3.0, 6.8 )
  33.         << QPointF( 4.0, 7.9 ) << QPointF( 5.0, 7.1 );
  34.     curve->setSamples( points );
  35.  
  36.     curve->attach( &plot );
  37.  
  38.     plot.resize( 600, 400 );
  39.     plot.show();
  40.  
  41.     return a.exec();
  42. }
To copy to clipboard, switch view to plain text mode 

13) in the .pro file of your application include this line: include (C:\Qwt-6.1.3\features\qwt.prf)

14) run qmake, build and run, it will work now, so this way if you are building 64bit programs with MSVC, they will be able to work with your 64 bit MSVC built Qwt plot libraries.

NOTES: * Again, I did not need sliders/knobs or QtCreator integration, so I turned it off. If you are also fine with this then this manual is for you
* pay attention at step #7, you must provide "amd64" argument to that .bat file, in order to make it 64 bit. Let the "amd" word not confuse you (as it did me and I lost some time with this) because even x64 platform also defaults to amd64 in that BAT file.