To use YouTube AdAway, you need to have Xposed installed on your device. The process for installing Xposed is relatively simple and the app necessary for doing so can be downloaded from Uptodown. However, you should note that it's necessary to restart your Android after installing and activating YouTube AdAway in your list of Xposed modules.
YouTube AdAway is a pretty interesting app that, like all apps of its kind, is a real double-edged sword. After all, if you're going to watch a video, it's because you're interested in its content. And if you enjoy a video, then maybe it would be reasonable that the video's creators receive the money from those ads.