I don’t put my markers [I]on[/I] my stitches, so in order to later follow the directions exactly for Row 5, I would put my marker before the K1 in the row you just described. So, K14, M1, place marker, K1, M1. When you have to place markers later, you can do the same - place the marker [I]before[/I] the last stitch.
However you do it, on Row 5, you want to knit through the M1 of the previous increase row, the M1, K1, M1 on the K1 stitch of that row.
As for your cast on, that usually doesn’t count as a row.