FYI, this forum is for general discussions; in the future, post OJS questions in one of the forums specific to OJS.
Are you looking to upgrade your installation, taking content with it? If so, see docs/UPGRADE, which is shipped with OJS.
Are you looking to move content from one installation into another that already has other content? If so, the best way to do that is with the Articles & Issues XML plugin, which is included in OJS and available in the Journal Manager's "Import/Export Data" area.
Public Knowledge Project Team