NOTE: Mitel Software Installer requires Windows 7 Professional (will not work on Home!) or newer (Windows 10).
Also note: When clicking link above it will bring up new window with Google Drive "DOWNLOAD" button, click the DOWNLOAD button to get the file, then install it.
Below are some sample pictures of a Mitel 5312 IP phone, showing buttons on front, as well as handset and switch/data port jacks on bottom/back.
Mitel AX - Sample U-CLIP to secure AMPHENOL cable