Check the shirt sleeves against the pattern to check for the front and back of the sleeves. With right sides of the fabric together, lay the sleeve on top of the shoulder with the center of the sleeve lined up with the shoulder seam and the front of the sleeve facing the front of the shirt. Set the doll shirt on top of paper to control the stitching, (see tips in the last step) and place your sewing machine needle into the seam line at the center top of the sleeve (close to the shoulder seam line. Start sewing the seam of the arm sleeve, stitching from the center top of the arm towards the side front of the shirt, shaping the sleeve edge to the armhole edge.
Repeat for the back of the sleeve, using your fingers or a toothpick or pin, to adjust the fullness of the sleeve to fit the armhole. If your pattern has full arms, you may need to baste the tops of the sleeves along the seam line to 'gather' them so that you can fit the fullness of the top of the sleeve into the armhole. Remember that this is your first real test of your basic pattern, and you may need to adjust your armhole opening, making it smaller or cutting larger sleeves. If you have to adjust your fabric to fit in a sleeve, remember to transfer any adjustments to your basic pattern so that your next shirts will not need adjustments.
Set the sleeve into the armhole of the other side of the shirt, taking care to make sure the sleeve front is facing the front of the shirt.
When the sleeves are set into the armhole, test fit the shirt on the doll to check the fit of the top of the sleeves against the doll's body. Adjust the sleeves (and your main pattern) if necessary.