Chord Chart Available in Songbook
If you are playing this on acoustic guitar then I would recommend playing the full barre chords in a bass / chord strumming pattern. The best way to learn that would be to watch Bruno Mars perform it on his acoustic guitar in the Billboard live performance. Keep in mind he is playing it a whole step down ( two frets ) so the Key of the song is A Major. For the regular version on electric guitar I would play only on the top 3 strings, clean tone, and a sharp attack for the reggae rhythm guitar.