Complex sentence: If you drape the wrist, swing the arm to the strings and touch the i finger to the strings, then roll the arm on the guitar until the m finger touches the strings, and this is "the angle of the fingers to the string".
Split into simpler sentences: If you drape the wrist, swing the arm to the strings and touch the i finger to the strings. Then roll the arm on the guitar until the m finger touches the strings, and this is "the angle of the fingers to the string".