stereo wont unlock

i have a 97' cavalier and i recently just changed the battery and when i did, it locked my stereo. I have the code to unlock but i dont know how, and i lost my owners manual so i have no idea what to do. I heard u had to hold am/fm and three 0's are suppose to come up but ive tried holding it for a minute and got nothing at all except the same LOC thing that always comes up, i also heard about hitting the hr/min button and all i get when i hit that is InOP, and i dont know what that means either. The InOP thing is weird to because i used to be able to atleast punch in the numbers then, but thats all that comes up now. Anyway, any help would be very much appreaciated. Thank You

beat the damn thing a few times and then take it to the dealer. You shouldn't of stole the radio though man. what are we gonna do with you