After running the installer Reality is not installed in Studio
This can happen if the folder where DAZ Studio is installed is write-protected. In this case You need to change the access rights of that folder.
To do so, use the file manager of your operating system.
For OS X you need to right-click on the Studio folder and select Get Info. From that window give yourself the rights to read and write to that folder and all the included subfolders.
If you're using Windows, use the Windows Explorer, right-click on that Studio folder and select the properties menu. From there give yourself read and write access rights for that folder and old included subfolders.
After changing the access rights run the installer again.