The complete manual can be found here:
http://feelyoursound.com/melodicflow-manual/

Depending on your DAW and your operating system you will need to copy the plug-in to a different location. The most common locations are:

Windows (32 bit DAW): Copy the file MelodicFlow.dll to the folder "c:/program files (x86)/Steinberg/VstPlugins/" (this is the default for most 32 bit DAWs).

Windows (64 bit DAW): Copy the file MelodicFlow_x64.dll to the folder "c:/program files/Steinberg/VstPlugins/" (this is the default for most 64 bit DAWs).

Mac OS X: Copy the file MelodicFlow.vst to the folder "/Library/Audio/Plug-Ins/VST/".

MelodicFlow acts as a VST instrument inside your DAW. It receives notes like any other VST instrument, but won't generate audio signals. Instead it creates MIDI notes which must be passed on to another instrument to hear anything.

Please consult the manual of your DAW to find out how you can pass the MIDI note output from one VSTi to another plug-in. 
Some pointers can be found in the online version of these setup instructions.