How to restore from an IPSW file on iTunes 12.3?

[iPhonePhreak]

I urgently need to restore to iOS 8.1.4 in order to successfully upgrade to iOS 9, but this new iTunes doesn't even give the option to locate the IPSW on the computer then restore from it. What do I do?

 

[MacManiac76]

Hold down Option (Mac) or Shift (Windows) while clicking on restore in iTunes.