"Lei suona il flauto da quando era giovane."
Play is "giocare" when it refers to the act of playing a sport, a game, with a toy etc. Play is translated as "suonare" when it refers to play a musical instrument.
EDIT: sorry, seen the reply below I think I misunderstood the question.
I think those, who reached this exercise should already know the difference between giocare and suonare. :) But thanks anyway.
If you are asking why "suona" (presente in Italian) is translated to "has played" (present perfect tense in English), it is because Italian uses present tense since she is still playing the flute, while English uses present perfect because the action started when she was young. It wouldn't be correct to translate it as: "She plays the flute since she was young."