The distribution file for the IBM WebSphere Portal Server 6.0 agent is a .zip archive named websphere_v60portal_agent.zip. After you download the file, unzip it using the appropriate utility or command for your platform. For example, on Solaris systems:
unzip websphere_v60portal_agent.zip
For more information see, Preparing to Install the IBM WebSphere Portal Server 6.0 Agent.