Play both the left hand chord and the bottom note of the arpeggiated chord together on the beat. The remaining notes of the right hand chord then follow.
Experiment with the speed. Sometimes playing arpeggiated chords slowly (spreading them over the full time value of the chord) can be quite lovely.
Sometimes one arpeggiates a chord so as to fit the hand (the span may be too large). In such cases it makes sense to play the arpeggio as fast as possible to simulate a chord.
But sometimes (and I believe this to be the case, since the span is not a problem) one arpeggiates to single out each tone and yet overlap them in order to manipulate the overtones. Much of Debussy's music is about overtone manipulation.
I suggest you listen to a variety of pianists playing this piece (my favourite Debussy interpreter is Walter Gieseking)
Best wishes,
Bernhard.