This scan sounds like a big event, but most of getting ready is small and sits on your side of the appointment: what you wear and when you last ate.
The short answer
Wear clothes that have no metal in them. MedlinePlus says: "You will be asked to wear a hospital gown or clothes without metal zippers or snaps (such as sweatpants and a t-shirt)." You may also be told to skip food and drink. MedlinePlus adds: "You may be asked not to eat or drink anything for 4 to 6 hours before the scan."
Note the wording. The page says you may be asked, so the instructions from your own imaging team come first.
Making it easy
Sweatpants and a t-shirt need no shopping trip and no skill, and you can choose them the night before. For the fasting window, count back from your appointment time and plan your last meal around it. Readers heading to a scan from Wood Dale or nearby can do the same count once they have the appointment time.
Questions for the imaging office before scan day
Call the imaging office and ask whether they want you to fast. Ask whether you should change clothes there or arrive ready. If something in your instructions does not match what you read here, follow the office and ask them about the difference.
To read ahead, MedlinePlus has a page on the leg MRI scan and another on the joint x-ray. RadiologyInfo.org covers musculoskeletal ultrasound. The study MRI evaluation of traumatic and non-traumatic pathologies of the ankle joint and hindfoot is open to anyone who wants the research.
A note for a first scan
If this is your first MRI, the preparation fits on a sticky note: clothes without metal, and a question about eating and drinking. That is a short list, and you can handle it.