The original Flappy Bird game has unfortunately been revoked by its creator after he received a large amount of harassment about the game. While it is no longer available for new players, you can download any one of a number of clones. This can be done through the app store, Android market or Google play.  Some notable clones include: Silly Bird, Flappy Fish, Flappy Hipster, Fly bird, Tappy Nyan, and Flappy Bert (from Sesame Street)! You can also download the original game, but you will have to find it on the internet and install it manually. Just be sure to use a reputable website! The creator has recently stated that he will someday bring the game back to official channels, but that that will not happen any time soon. This game will require immense concentration if you wish to achieve a high score. This can entail the removal of pets from the room, lowering of music volumes or not sitting on an aisle seat whilst playing on a bus, for example. However, everybody has their own methods to increase levels of focus. Try experimenting with various external factors to find what suits you best.

Summary:
Download the app. Eliminate any potential distractions.