In most places, including Nassau or Suffolk County, you will need an attorney to go to court with you. However, the requirement that you "pay back 5 times the amount to the store" is not part of your criminal case. The store hires lawyers to try to collect that money. You have no obligation to pay that money unless you are sued by the store; on the other hand, you might want to pay it to avoid future lawsuits -- always consult with an attorney when making these decisions.
As to the criminal case, you always enter a "not guilty" plea on your first court date. You then have the right to proceed as if your case was going to trial, or to work out a plea bargain for a lesser charge. If you choose to make a deal, you will most likely have to do some community service and pay a fine and some court costs to receive a plea bargain offer that will not give you a criminal record.