To run Libro Game Creator you need Java installed. In the weird case you don’t have it already, you can download Java from https://www.java.com/it/download and follow the instructions to install it.
LGC needs Graphviz to generate gamebook’s graph. The program could be downloaded from http://www.graphviz.org/Download..php
To install LGC download the file (.zip or .tgz), uncompress it on your PC, anywhere you want, and run the correct launcher:
run.cmd on Windows systems
run.sh on Linux systems (you need to make it executable before you could launch the script)
If you have problems with launchers, try running lgc3.jar instead.