See the wiki.
First install Qt 5 and KDE Framework 5 headers. On Debian and its derivatives it can be done with:
apt-get install extra-cmake-modules qtbase5-dev libkf5coreaddons-dev \
libkf5i18n-dev libkf5xmlgui-dev libkf5doctools-dev libkf5kio-dev
Then run cmake:
cmake -DCMAKE_INSTALL_PREFIX=/path/where/to/install
make install