Enter a plea of not guilty and then you will be given a court date at which time your attorney will hopefully be able to negotiate a positive outcome for you. You should contact an attorney immediately and discuss any defenses and what you options are.
The first thing you have to do is respond to the citation. There are instructions on the back of the citation for doing that. Contact the office of the MDJ where the citation was filed. Ask when you can appear at the MDJ's office, enter a plea of not guilty, and post whatever collateral the MDJ requires. Since the fine and costs are not specified you can mail a not guilty plea in with $50 collateral but if you appear in person the MDJ may allow you to post less. After you have responded to the citation you should speak to an experienced criminal defense lawyer. If this third offense was committed this year you may be facing up to a $1000 fine, 90 days in jail, and a 2 year loss of motor vehicle operating privilege. Good luck.