You can print a Voter Registration Application and send it to the Registrar of Voters. The form is available on the Secretary of the State's web site:
https://portal.ct.gov/-/media/SOTS/ElectionServices/ElectForms/electforms/VoterRegCardEnglish2015.pdf
Please mail the completed application to:
Registrar of Voters 479 Main St. Manchester, CT 06040