Go to the Colorado State website. http://www.courts.state.co.us/Forms/Forms_List.cfm/Form_Type_ID/15
You need to file a Petition for Allocation of Parental Responsibilities. All the information needed can be found on the web site. Your chances of getting sole parental responsibilities are good because the father has not played much role in the child's life and is in jail.
Sign up to receive a 5-part series of useful information and advice about child custody law.