To get the full version of the Fingerdash song, you need to search for "Fingerbang" by MDK, as it was renamed for its inclusion in the game. The full track is available through official channels like the MDK YouTube Channel and Spotify .
While not on Newgrounds, you can download it via SoundCloud or find remixes on Newgrounds . To use it in game, you must manually replace the song files on your PC. Fingerbang (Fingerdash from Geometry Dash) - Spotify