This is given for collecting 100 coins total in all games played. The easiest way to get this is to just play the first level. Collect the easy coin given, and then quit and restart. From my experience, you do not even have to complete the level, just get the coin.
If you want to feel like you are accomplishing something, use the time to attempt to complete the Sharp Shooter achievement. (Grab the coin on the level 1-1 games that you miss the 0:05 mark, restart and try again). Most likely you will get the 100 coins before you get the 0:05 (unless you are lucky as I was).