I have installed the panels, but I can’t find them in Windows > Extensions menu
You have installed the RA panels through the correct Adobe Extension Manager, and the dialog window in it stated:
Once this extension is installed you will find it in Window > Extensions > BEAUTY RETOUCH
If you have re-started Photoshop, but still don’t see the panel in the menu, please make sure you have installed the correct .zxp file via the correct version of Adobe Extension Manager or ZXPInstaller for your version of Photoshop.
If you have installed it via Adobe Extension Manager CC2014 – the Panel will be installed in your Adobe Photoshop CC2014 not in Adobe Photoshop CC2015 or CC (version prior CC2014) and you will see it in the Adobe Extension Manager CC:
So, make sure you used the correct version of the installer (Adobe Extension Manager for CS6 and CC2014 and ZXPInstaller for CC2015) and its version is matching the Adobe Photoshop version.