Hello blrmisc,
the product's install location can't be changed. The button is there because of Apple's bug in Installer, that causes it to show even if the package says it can't be installed to custom locations.
If you double-click the package to start new installation flow, you should be able to install the product just by clicking 'Continue' or 'Ok' at every screen. Or are these buttons disabled for you at any moment? If so, please hit CMD+L while the installer is open and you should see logs explaining possible issues.
Best regards,
Jakub
