inSSIDer checks for and updates automatically while it is running. If a new update is available, you should see a notice in the lower right of the app window that you can click to restart app and run new version. You may need to run inSSIDer for a minute or two for the download and update to occur before the notice displays. Also, the newest inSSIDer versions can be downloaded from the standard download link at https://www.metageek.com/support/downloads/download-inssider-win.html