The conversion process is pretty simple. If your account needs to be converted, you should be prompted to do so when you login, or you will see a message prompting you to do so in the notification drop-down at the top right of the page, then simply follow the prompts to transition your account to whatever service you prefer.
The account conversion workflow will close on April 30, 2013. If you have not updated your account by April 30, you will be required to make a new account to interact with the community. Creating a new account will cause you to lose your comment history.