How can we get my boyfriend's jail tiome concurrent to his previous charge after receiving an additional months on jail time?

You cannot change the sentence once it is given. You must appeal it now and that will not be successful in this case if it was a legal sentence.

In most States crimes that are committed while in prison. (As I assume that this one was) are mandatory consecutive to any sentence that they were serving when the crime occurred. If this is the case where he is incarcerated then nothing can be done.

The best way to find an attorney is through a referral from a friend or relative. Otherwise, look through the yellow pages or google "criminal attorney" with your city and state.

It sounds like the 8 month sentence should have automatically merged with the 10 year sentence if it was imposed by a judge in a criminal court. If the 8 months was imposed by the Dept. of Corrections as a "loss of jail time", that's a different issue and the remedy would be an administrative appeal followed by an Article 78 proceeding in court if the appeal fails.

Look for a very experienced criminal defense attorney in your area. Check for referrals, how many years in practice, if they are part of any professional organizations. Most importantly is how much of their practice they devote to criminal defense. You want someone who at least devotes a substantial portion (at least 2/3 to 3/4 ideally). What you don't want is a dabbler or a general practioner. Ask some of the judge's clerks who they recommend as they see tons of lawyers on a daily basis good, bad, and mediocre. Good luck.