Do you need to do anything to prepare for my ultrasound?

Maybe. Call lab you are going to or check out radiologyinfo.Org about your test.
Ultrasound prep. Not sure what type of us you're going to have. If abdominal or pelvic, often you are required to fill your bladder (by drinking plenty of water) and not urinating until the study is done (full bladder allows a better image of structures). If other type of us, please specify, or contact the imaging department to find out what prep is required.