First off, make sure AutoPencil is on (select "Settings" and then "Helpers" to turn it on). Start a single player 'Timed' 6x6 on Easy. Now you will notice in the empty box you are highlighting that one or two numbers are black (or darker colored on some puzzles) and the rest are grey. The answer is the black one. Sometimes there will be more than one black number so u can come back to it, but on easy it shouldn't happen often and you can usually figure it out pretty quick. So use the right stick to select the black number and keep doing this until the puzzle is solved. And this technique is what you will be using from now on.
And for this task, in timed mode you start off with 3 minutes on the clock and a puzzle like this will take between 20-40 seconds. Just don't let the timer get to zero and that counts as one completed puzzle. Just rinse and repeat 9 more times for the achievement.