Measure 5 of the Moonlight Sonata Adagio Sostenuto is where the melody finally gets introduced.
But, only the first little bit, on beat 4. You can see this because the stems on the notes on measure 4 go in different directions.
To play it, you need to think that your right had has been divided in half and the thumb plays the lowest notes where your pinkie plays the highest notes at the same time.
Pay attention to beat one of measure 6 in the left. It has b sharps. It's a really common error to play either a b key or a c sharp key instead.