Need help installing Qwt

[Computer Hater]

First of all, I was talking about "project file" (myfantasticqtproject.pro): I supposed that you own a Qt project where you want to place some Qwt stuff; Makefiles are another kind of file that you should not care about.

Right. That was a stupid typo on my part. I meant I had edited my project file to include "CONFIG += qwt", not the makefile. And the project file didn't already have a CONFIG line, so I added the first CONFIG statement there.

If you installed qwt on its default target (C:\Qwt-6.0.1\), then you need to run 'qmake -set QMAKEFEATURES C:\Qwt-6.0.1\features' just one time and its doesn't show anything on output. Checking that qmake has successfully recognized the features path is possible with command 'qmake -query QMAKEFEATURES'.

Okay, I checked with the query command and it shows the features folder. So that part worked.

Maybe you didn't compile the examples, try to check that inside 'C:\<path of your qwt sources\qwtconfig.pri' the line QWT_CONFIG += QwtExamples is uncommented. If so uncomment that line then rebuild qwt.

That line is uncommented. However, inside my "C:\Qwt-6.0.1\" folder there are only the sub-folders "doc", "features", "include", "lib" and "plugins", none of which contains the source code or project files of the examples. Those are still in the source folder on my desktop. Hence my question if that source folder should have been placed somewhere more permanently and stick around as a source for the Qwt example projects. Up until now I had thought the examples would be copied into the installation target along with the rest.
Some of the other folders and files from the original source location are also missing.

What would I do ? Copy the examples manually to somewhere else or reinstall from another source location ?

Finally you're ready to go: try to add to your project a widget that shows a simple QwtPlotCurve.

The thing is that Qt Creator's source code editor doesn't seem to recognize anything starting with "Qwt" and the design area doesn't offer Qwt widgets.
I suppose I have to execute the last paragraph from the Qwt INSTALL file first:

For using the designer plugin you have to configure the Qt designer/creator
where to look for plugins. This can be done by setting the QT_PLUGIN_PATH or
using a qt.conf file ( see http://doc.qt.nokia.com/4.7/deployment-plugins.html ).
Beside the plugin the Qwt library itsself also needs to be known to the Designer/Creator
( see LD_LIBRARY_PATH, PATH ... above ).

The given link says QT_PLUGIN_PATH is an environment variable. In my project's environment variables there wasn't a QT_PLUGIN_PATH variable, so I set it.
The Projects menu in Creator then specifically said:
Using System Environment and
Set QT_PLUGIN_PATH to C:\Qwt-6.0.1\plugins\designer\

I tried it with and without the \designer sub-folder, but it is still not recognized.

Now in the Qt Plugin section it says that the Qt version number must not be lower than the plugin version number. My Qt version is 4.7.3. But where do I find the plugin version ?

Also, it says:

When building plugins to extend an application, it is important to ensure that the plugin is configured in the same way as the application. This means that if the application was built in release mode, plugins should be built in release mode, too.

I don't think I have "built" the plugin yet.
Maybe the problem is still with why the examples are not installed and the rest will fall in line ?