The WebSphere installation instructions used to be included in the user interface while installing Inspector. That information is no longer included, and needs to be added to the documentation.
Resolving the problem
The Installing with IBM® WebSphere Application Server topic in the Infocenter should include the following steps:
14. Click Configure. The Download Inspector.properties file page opens.
15. Save the inspector.properties file to the WAS ROOT\AppServer\properties directory. By default that directory is found in C:\Program Files\IBM\WebSphere\AppServer\properties.
16. Restart the WebSphere Application Server.
17. After restarting the WebSphere Application, go back to
http://<<WAS_HOST>>:<<WAS_PORT>>/inspector. The login page opens.