I Don't Know How to Love Him was sung by the Mary Magdalene character in Andrew Lloyd Webber's Rock Opera, Jesus Christ Superstar.
That I came to sing this myself came surprisingly (for me that is) in 2006 as a bass singer in Die Zeitlupe. The bass part befittingly is dowsed with "doo doo"'s complementing the delightful upper voices.
This SATB version in an F♭-major arrangement by Henry O. Millsby can be found in 4 Voices published by Edition Helbling.

Lyrics