A site archive may be imported via the Site Archive tool in the Administration Workspace, or into an existing site via Worksite Setup.
Unzip/uncompress the archive (depending on archive format) to a directory in $CATALINA_HOME/sakai/archive. This depends upon access to the server upon which Sakai is running. The "sakai" directory is the same directory that contains the properties file(s), typically sakai.properties or local.properties. "archive" is a subdirectory you need to create within the sakai directory.
Select the Site Archive tool from the Tool Menu in the Administration Workspace.
Select the Worksite Setup tool from the Tool Menu in either the Administration Workspace or My Workspace.
After the last step in the site creation process, you will have the opportunity to upload an archive.