You do not need to press memo. All memo does it turn on the chime that beeps 3min before the hour changes. When you first turn the car on there should be a little dot flashing in the display between the hour and min. This lets you know that the time can be changed. To set the time press the h/dat button untill you get the correct hour, it will do am and pm so watch for that. With the dot still flashing press min/dat to set the correct min. Once you get that set press the hour button the dot will stop flashing letting you know the time has been set. To set the date press the date button if the dot isn't flashing press and hold the date button then the dot will start to flash, this works for setting the time too just press and release the houur button then hold the hour button. Once the dot is flashing press the h/dat button untill you get the correct month, then press the min/dat button untill you get the correct day. Also look on the back to make sure your display is switched into the correct units for your country, either C for Celsius or F for Fahrenheit.
Also another thing about the memo button, it will not say memo in the display. All the display will show if the memo button is pressed is something that looks similar to this, .)) excep the dot is centered not at the bottom.