Browse your computer to select the local IPSW file you previously downloaded.
In this guide, we will reveal the locations for 3uTools IPSW files, how to change the default directory, and how to recover precious disk space. 3utools ipsw location top
Open and go to Settings (usually under the three-line "hamburger" menu in the top right). Look for the General or Firmware tab. Browse your computer to select the local IPSW