The pattern set up is the two rows:
where the 6sts in the middle set up the cable.
The pattern instructions and row to turn the cable are given in the chart. It reads down one column, then skip to the top of the second column, work down that column, skip to the top of column 3, etc. So you'll have Row1, Row2, Row3 is a cable twist row (C), Rows4-12, Row13 is a cable twist, etc.
It's written out this way so that you can check off each row as you complete it and that's one way of keeping track of which row has the cable in it. You could also use a row counter. After awhile, you'll be able to judge where the cable goes especially for patterns with fewer rows between cables.
(see also the numbers 1 2 3 4 near the initial cast on where you can check off the knit rows as you do them)