Before you can start using SchemaSpy you must have installed two things in your system environment.
Download instructions for all operating systems: https://java.com/en/download/manual.jsp
Since version 6.1.0 Graphviz is no longer required. There is an embedded viz.js that can be used by adding command line argument
The easiest way to install Graphviz is to download the msi package from http://www.graphviz.org/download/
Remember to add the folder containing Graphviz's dot.exe application to your system PATH variable, eg.
C:\Program Files (x86)\Graphviz2.38\bin
- Linux, Mac OS
Please read carefully the detailed instructions on how to install Graphviz on your os version http://www.graphviz.org/download/.
SchemaSpy is just a single executable jar-file (schemaspy-[version].jar), you can download releases from http://schemaspy.org or the github releases page https://github.com/schemaspy/schemaspy/releases
If you feel adventurous there is a link in the README.md for latest builds.
When you have your jar-file head on over to Get Started