We no longer move accounts from Justin.tv to Twitch as of May 31, 2013. This option to move to Twitch was removed from JTV in December 2012. We believe this to be enough time for users to have requested a switch.
As JTV and Twitch share the same user database, you will need to create a new account on Twitch to use our site.
FYI: Deleting your account on JTV will not allow you to recreate the account on Twitch. The account will remain in deleted state. We do not clear deleted accounts.