Bonita Open Solution is available from the Download BPM software and documentation page at www.bonitasoft.com, at http://www.bonitasoft.com/products/BPM_download_all.php
When the zipped folder has been downloaded, extract all files.
Open the unzipped BOS 5.6 folder
Launch the BonitaStudio application file for your operating system.
See here for more details about hardware requirements and software requirements.
NOTE: You will need Java Runtime Environment 6 with BOS 5.6.
To install and configure Bonita Open Solution for a distributed or production environment, see System Administration.