This is usually attached to the violin when the violin is built. Aside from that, be sure you have some rosin (coagulated sap) for your bow, a music stand, and a book of beginner lessons or songs, preferably in a format that will open flat. Some violinists, especially beginners, also purchase a shoulder rest, which is a violin-width pad that sits on your shoulder underneath the violin and makes it easier to hold. Many people start with a shoulder rest and eventually remove it after a few years.