You can go to court, with or without a lawyer, and plead not-guilty. Then, you cannot be convicted without a trial. (The trial will not take place at the First Appearance.) Criminal possession is not quite the same thing as "they belong to me." Sometimes mere knowledge of the presence of contraband can be enough for criminal possession, depending upon circusmtances. It's valauble to keep your record clean, even your juvenile record. You will normally do far better with a lawyer. You may be able to get a Public Defender appointed to represent you, if you apply.
From what you have described there would be a lot of things I would want to investigate, such as why the police felt they had the ability to search the vehicle and how they claim the liquor bottles should be your responsibility. This seems like a questionable charge and you should speak to an attorney about it. A prosecutor may give you a deal because of some of these facts, but i highly doubt they would dismiss the charges unless you had someone aggressively defending you.
A thorough review of all the facts and evidence would be needed in order to determine all the defenses that may be available to you in this particular case. After these defenses are discovered, then you can begin negotiating with the prosecutor with the hopes of eventually getting the charge dismissed to preserve your record. There may also be legal reasons why some, or all, of the evidence could be excluded. If you have not retained an attorney at this point, it is advised that you do so (or apply for a public defender is you qualify).
Depending on the facts, there may be several options in this case.
I hope you find this information helpful, and feel free to contact me if you have any other questions about your case. I wish you the best of luck.