I had to learn this the hard way! There are NO instructions out there.
Steps:
1 - Click MENU
2 - Click SETUP mode (next to MENU, there are 4 icons....push the one that has two tools on it.
3 - Look at the screen (little clear window on top of the MX452)
4 - Depress right arrow to second setting - "DEVICE SETTINGS"
5 -Puh OK
6 - shows print settings so click RIGHT ARROW to LAN SETTINGS
7 - Hit "OK"
8 - You'll see "WLAN -activ/inactiv" Click "OK"
9 - With right arrow - Choose INACTIVE
10 - Click "OK" - the blue light will go out.
11- To restore INCATIVE...just repeat steps and Choose ACTIVE
