First download OpenXava from
openxava.org or from
SourceForge.
Choose the appropriate distribution for you operating system.
Then uncompress the file you have
downloaded, a zip or a tar.gz file, in any folder of your computer.
Finally, execute openxava.exe
(for Windows), or openxava (for Linux and Mac). In the Mac case
maybe you Mac refuses to execute it when you click on it, in that case
open a shell and type the command ./openxava. You can find this
file in the root of the folder where you have uncompressed OpenXava.
For versions previous to 6.4 you
don't have openxava.bat/sh, instead open the quick-start.html
with your browser and follow its instructions.