Bernat bunny toy

Hi

I need help with a knitting project, it says after casting on 46 sticthces and work in stocking st for 4 inches , do arm this is the problem it says to cast on 17 sts beg next 2 rows 80 stitches, DO I cast on 17 stitches then how do I get to the other side to cast on 17 more stitches? Help would be appreciated.

Cast on the st at the beginning of the row, work the new ones and the rest of the sts on that row, then cast on at the beginning of the next row.