I've got the code but how did i put it in

To reset from 7SAFE , press AS plus the ON button (at the same time) and leave SWITCHED ON ....UNDISTURBED for as long as it takes to automatically reset itself (usually an hour or two)

.It is displaying SAFE because wrong codes have been entered ....so  it looks as though 1234 is NOT the correct code

If you have now been given the correct code then the code entry instructions depends on the MAKE + MODEL of your radio ....but as you have an AS button to press then try these instructions

Switch the ignition key ON

Press and hold AS button *  and the  ON button at the same time

Display Shows SAFE  then goes to 10 - - - - with a "Beep" from the speaker

Press Preset Button " 1 "repeatedly until the 1st Digit of your Code is displayed
Press Preset Button " 2" repeatedly until the 2nd Digit of your Code is displayed
Press Preset Button " 3" repeatedly until the 3rd Digit of your code is displayed
Press Preset Button " 4" repeatedly until the 4th Digit of your code is displayed

If the display  now shows the correct Code number then

Press  Button AS  and hold to Enter and if successful  there should be a "Beep" from the speaker and the radio should switch on

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If these instructions do not work on your radio  , then find your MAKE+MODEL of radio on this free  Code Entry Instructions website 

http://www.radio-code.co.uk/code-entry-help.php