Reading this sheet
The first line holds the two-note pickup and the first full bar; from the second line on, each line is exactly one bar. Every character is one sixteenth note. The melody lies high: f is E5 (the second E above middle C), D is D♯5, a is B4, d is D5, s is C5 and p is A4. Capitals mean black keys, so D is Shift+d, and W and O are the two G♯ keys the tune borrows from E major.
The left hand plays from the number row and the e key: 6 0 e spells an A minor chord upwards (A2, E3, A3), 3 0 W an E major one (E2, E3, G♯3). Where both hands begin a bar at once, the sheet brackets them: [6p] is A2 with A4, [3a] is E2 with B4, [6s] is A2 with C5.
Three octaves under your fingers
From the lowest note, E2, to the highest, E5, the opening spans three octaves, more than a phone shows at once. On a computer screen the whole range fits; on a phone the keyboard travels with the music, and the wide brackets like [3a] are taken one note after the other.
Practise the melody bars and the arpeggio bars separately at first. The rocking f D f D f wants a light, even touch; on a computer keyboard, keep a finger resting on Shift for the D sharps. The arpeggio bars are a shape: low, middle, high, then the melody takes over.
About the piece
Für Elise is Beethoven’s Bagatelle in A minor, WoO 59, dated 1810. It did not appear in his lifetime: Ludwig Nohl first printed it in 1867 in Neue Briefe Beethovens (Stuttgart: Cotta), from a manuscript that has since been lost, and who “Elise” was remains uncertain (IMSLP). The bagatelle is far beyond any copyright term.
The same letter-and-capital system is explained key by key on the piano sheets layout page.