Installation instructions are on the website: https://qwebirc.org/installation
If you'd like to make modifications you'd find it a LOT easier if create the following symlinks:
- js -> static/js/debug
- css -> static/css/debug
with a command like
cd /path/qwebirc
ln -s ../../js static/js/debug
ln -s ../../css static/css/debug
... then you can browse to http://instance/quidebug.html and use your favourite javascript debugger, as well as not having to compile each time you make a change!