Hi and welcome to Knitting Help! These directions are for brioche stitch
which gives a fabric that looks like Fisherman's Rib
but is worked differently. You could look at the directions on the brioche site together with the definition
for more about brioche. And of course, you could always follow the instructions for Fisherman's Rib if you prefer.
The directions for row 3 could be simplified to:
[knit the stitch that was slipped in the prev row together with its yarn over, yo, sl 1 purlwise] across. You should be knitting the slipped stitch together with the yo from the previous row, then makng a new yo and finally slipping the knit stitch from the previous row.