You don't go to a trial for an Article 15 unless you request a trial or court marshal. An Article 15 is a summary charge handled by the company commander.
A soldier has the right refuse to accept an Article 15 and instead request trial by court-martial. It is important to know that accepting an Article 15 is not an admission that you are guilty. ... A punishment by court-martial can be much more severe. so you will want to make this decision carefully.