Bind off on the right edge on the rows I listed and also, in some cases bind off on the next row on the left edge. For example, bind off one stitch on the right edge on row 9 and one stitch then on the left edge on row 10. A table with columns for the rows at each edge will really help keep these decreases in order.
You’ll always be casting off at the beginning of a row. In the example above, cast off at the beginning of row 9, work to the end of row, turn, cast off on row 10, then work to the end of row.
You could work the cast offs on the same row but it’s a fiddly technique that really is unnecessary. Casting off at the beginning of a following row works quite well and the tiny difference in row height is usually not even noticeable.
One other thought, you might consider using the sloped bind off here. I don’t know if there is a finishing edge on the sleeve but this gives a nice, smooth line to the bind offs.
https://www.youtube.com/watch?v=A3rD1v4NbKQ
Is the pattern from a yarn company or does it have a publisher listed?