The string closest to the floor is string 1 (shown as the top line on tablature by the way). The string closest to the ceiling is string 5 (the bottom line on tablature), which is that funny short string (the one that ends at fret 5).
String 1 = D String 2 = B String 3 = G String 4 = D String 5 = GPractice, take it slow, learn to play on time. Playing on time is more important than speed, more important even than playing the correct note.
Then there is the business of reading music. Most banjo music is passed around in tablature rather than in standard music notation. Tablature indicates which fret to hold down to play each note. It also indicates the time signature of each note.
Music is broken up into measures, and all the notes in a measure total up to a full time unit (i.e. they add up to one!). So a measure might contain four quarter notes, or two half notes, or a half note and two quarter notes.
That and a set of picks should get you started! (I'm only joking, a sensible person will get some introductory lessons from a good instructor).
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