You can either make your Hoodie long sleaves or short sleaves. If you make it short sleaves all that you have to do now is attach the hood. But if you want long sleaves then you will have to follow this step. Make two peices of duct tape (without the sticky side showing) that are as long as your arm and as wide as the sleave on the existing shirt. Then tape the edges of these together. If your arm is to wide then do what I did in the picture below to get some space. The first picture shows the second strip in progress and the first strip done.