Im 18 years old and i got caught stealing?

Ok well... im 18 years old i was caught stealing in walmart, they took me to the back room and searched me they found the item i stold and said they seen me take other things before. so i admitted to stealing two more little items. it all came to around $13 worth of stuff. After they made me fill out papers and asked for my ID. I dident have my ID so they called the police and they took me to jail for a few hours and i got fingerprinted and my pic's tooken.It was my first time going to jail or anything, After they me sent home after my girlfreind got me out for $12. and now i have a fee of $139 to pay back to walmart that they gave me in there backroom the police dident. but when i left the county jail they told me i had to go to court or the court and pay $12. i was confused and he sayed say you here for a pft or someting like that im not sure, but i just acted like i knew and left. Now im confused do i have to go to acuall court in a room with a judge or do i have to go to the courthouse and pay a fee or what im so confused?