The document needs to be notarized as well.
If you are a legal guardian, then you must include a copy of notarized guardianship documents.
You will need to have the Bill of Sale signed and notarized, then register the document with the title agency.
Though the grantor's signature does not always have to be notarized, it is recommended as an additional method of recordation.
Have the form notarized by a legal notary public, and save a photocopy of the form for your records.