Extract the workspace zip file to a directory (you have probably already done this).
If you are using a language other than English, you should open the VDF 17.1 Database Builder from the Windows "Start" menu (by default under "Visual DataFlex 2012 - 17.1" -> "Development Tools"). In Database Builder from the menu choose "File" -> "Select Workspace", navigate to the WebQuery workspace and open "WebQuery171.sws". Then from the menu select "Maintenance" -> "Reindex", then in the dialog click "Select All", then "Reindex". In the Reindex dialog click the lower of the two "All" buttons followed by the "Reindex" button - the process should only take a few seconds, after which you can close the dialogs ("OK" then "Cancel") and exit Database Builder.
Open the Visual DataFlex Studio (Note: if using Windows Vista or higher you should run the Studio via "Run as administrator") and from the menu select: "File" -> "Open Workspace", then navigate to the directory where you extracted the zip file to and open the WebQuery171.sws file.
From the Studio menu select: "Project" -> "Project Properties <WebApp.src>", then in the dialog, click on the "Web Application" tab and click the "Register WebApp" button followed by "OK". When it has finished, click "OK" to close the dialog.
Compile and run (F5) the WebApp.src project - further instructions are available in the application (or directly in WebQueryUsage.html), as well as a variety of examples of how WebQuery can be employed.