It is recommended to change the needle after 8-10 hours of sewing. You may need to change more regularly if you are using heavier-weight fabrics or regularly sewing through many layers.
Grab your new sewing needle. Typically, the shank (top part) of the needle has a flat side and a rounded side. Placing the flat side to the back of the sewing machine, insert the new sewing machine needle into the needle clamp, as high as it will go.