You can find many simple examples in the examples/declarative sub-directory that show how to use various aspects of QML. In addition, the demos/declarative sub-directory contains more sophisticated demos of large applications. These demos are intended to show integrated functionality rather than being instructive on specific elements.
To run the examples and demos, you can use Qt Creator or the included qmlviewer command-line application. It has some useful options, revealed by:
bin/qmlviewer -help
For example, from your build directory, run:
bin/qmlviewer $QTDIR/demos/declarative/samegame/samegame.qml