|Photo - Huffington Post|
According to the Secretary of the State's office, a voter's application "must be postmarked by the 5th day before a primary (OR received by your Registrar of Voters or a voter registration agency by the 5th day before a primary). You may apply in person to your town clerk or registrar until 12:00 noon on the last business day before a primary". This applies only to unregistered voters; it is too late to transfer from one party to another.
You may register to vote on line, here.
(but not for the primary).