I am not sure what they mean by "working in ends of rows, ch 1, mark last ch-1 made, sc in each row across" Can anyone walk me through that?

Working in the ends of the row are stitches you put up the side.

Reading the pattern you would finish your row, crochet one, then put a marker (safety pin or something) to the previous crochet, then single crochet down the side.

Let me know if you need me to send pictures of the technique.