The melody of All I Want For Christmas Is You by Lady A runs 212 notes across 52 bars, 2:38 long in Bb at 140 beats per minute. The tab sits low on the neck, mostly under the fourth fret, one note at a time — no chords to barre and no strumming pattern to keep up with. A piano backing track plays the chords and bass underneath, so the line you are learning sounds like the record even at half speed.
Prefer to strum and sing it instead? All I Want For Christmas Is You chords and lyrics.