In Massachusetts you need to file a Petition which is a form you can get from the Probate and Family Court or Juvenile Court in occasional circumstances.  Where the Court that has been making the custody and parenting schedule regarding your grandchild and in that Petition, you should describe not only your proposed visitation schedule, but you also have to provide some details; including your relationship with your grandchild and why it would benefit your grandchild to have visits with you.