If you can get it expunged, do so.
If not, when you address it in your applications, I would suggest that you stick to a basic explanation and an assurance that you learned from the experience and have taken steps to ensure that it won't ever happen again. Avoid any statement that could be perceived as making excuses or avoiding responsibility for what happened. Having reviewed internship applications myself, I would guess that the misdemeanor may raise some concerns, but you can at least avoid worsening the situation if you're careful not to blame shift.