The song primarily uses the chords D, G, Bm, A, Em and C. A good place to start would be to become comfortable with these chords and their transitions.
The song begins with a simple Intro where you move from D to G, then Bm and finally to A. Practice these transitions and try to maintain a smooth rhythm. The strumming pattern can start simple, with a down strum for each chord, and then progress to a more complex pattern such as down-down-up-up-down-up.
In the Verse, there is a quick transition from D to G and then to Bm and A. This may be tricky for beginners, especially the transition from G to Bm as it involves a barre chord. Take time to practice this transition to ensure it becomes seamless.
The Chorus introduces the C chord and a quick transition from G to Em to C and back to G. This could be a bit challenging for beginners. Practice transitioning between these chords until it becomes smooth.
In terms of strumming, both the verses and the chorus can use the same pattern as the intro, down-down-up-up-down-up. This pattern provides a gentle rhythm that complements the song's melancholic tone.
The Outro repeats the same chords as the chorus, so by this point, you should be comfortable with the transitions.
Finally, remember that the emotion in the song is just as important as the technical aspects. As you play, try to convey the longing and melancholy present in the lyrics.