Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Miami to Springfield, Massachusetts as you normally would.
For a flight from Miami to Springfield, you will be flying from Miami. Miami (MIA) is just 6.1 mi from the center of the city. Miami is the only Miami airport and it handles 0 outbound flights to Springfield per day. 30 airlines have flights to Springfield from Miami on a regular basis.