See more after the jump!
So here we go with those cute lil' cap sleeves! Lay both of your sleeves like so and trim a little bit around the edge so it's curved a little bit.
Next, sew a gathering stitch about 3 inches from the shoulder seam on both sides. (should be about 6 inches total, to make sure it's as evenly gathered as possible)
Should look like this.
Then pull the threads to gather until it looks good. (and even-ish)
This is how mine looked.
Then grab some more of your bias tape for the arms.
sandwich the arm holes and gathers in the bias tape and pin it like so.
Then sew that down, close to the edge.
Finally, pin and sew the side seams together, then finish the seams.