Yes, you'll only be placing 2 markers, each 18 stitches in from the end, although I think they really should be 9 stitches in from the end. Then whenever you get to them as you're knitting, you just slip them from the left to the right needle.
It also looks like there might be an error in the pattern because on Row 13 you are basically alternating K9 and P9, but then it says to P9K3P3K3 at the end, so you'd end the K9P9 repeats and do ANOTHER P9?
What pattern is this? Is it the "Baby Blocks" afghan from A Good Yarn
If so, I know there was a pattern error in the first edition of the book.
How many total stitches do you have in the row?
Hope this helps a little.
Happy Knitting :XX: