ACA NEOGEO METAL SLUG 2

You will likely earn this achievement right before completing the other score posting related achievement. To update the high score you simply must beat a high score on the board and then enter your name once you lose all your lives/continues. I beat out first place on classic mode (~107k points) by beating the team of helicopters and immediately after gave up my lives so I could post the score but it would probably be better to wait until after you score the million points that are needed to max out classic's score achivements so that you can stack all them all in one go