How do I enter an MMSI number into my Uniden UM415 It is useless to call Uniden, I have already wasted 3 hours on hold with them.

Hi Peter!
NICE radio Man. You're right, Uniden customer service is horrible.
Ok, here's the deal. You HAVE to get this right the first time, otherwise you pretty much have to send the unit back to Uniden.

Press and hold CALL until the setup menu appears.
Press ENT (1W/25W), that gets you to the user MMSI portion of the program.
NEW should be what you see on the screen.
Press ENT. That'll get you to where you actually get to enter your number.
Using channel up or channel down, set the first number.
ENT
The cursor moves to the next digit.
Repeat until your full MMSI number is entered and displayed on the screen.
IF YOU MAKE AN ERROR, don't panic, press clr/scan and the cursor will move back one spot to the left, erasing the wrong digit.
When the ninth digit is correct, press ENT. The screen will display your MMSI number and ask you to confirm. To save, select yes. To cancel, select no.
Before saving the number, your radio will ask one more time if you wish to confirm and warn you that this is a permanent setting.
Press ENT to confirm, or CLR to start over again.

Hope this helps.
-Steve