What could happen to me for a first time offense for retail fraud under $20?

I was charged with retail fraud (1st offense) and have no clue what to say in court. I admitted switching the tags to the employee however, the piece of clothing that I was trying to buy didn't have the sale tag on it, like the other ones did but in larger sizes. Since it was the same exact item, I just took a tag from a LG size bathing suit top and kept it with the item I was going to buy. I wasn't trying to make my own sale prices. I begged the lost prevention woman to go look at the other tops and she would see that those tags were the same one I had in my hands. I was in a super rush (late for a birthday gathering) and what I should've done was take the large top, along with the one I wanted to purchase, up to a cashier and allow her the time to look into this for me instead of taking the tag from a large and kept it with mine and went to a self check out. I had no time, the lines were long, and I knew it would take the cashier even more time to look into the price of my top. I therefore took it upon myself to just get the same tag off of another top! I don't know what to do. The person who I thought would represent me since they are long family friends but I'm not getting a response so I'm going into the court completely blind and have no clue what to even say or do.