At someone's first or second court appearance they are usually asked to state for the first time whether they are admitting that they committed the crime, or if they are denying that they committed the crime. Mainly, those two pleas are "Guilty" (Yes, I did it) and "Not guilty" (No, I didn't do it).
The official term for the accused (or his lawyer) saying "[I plead] guilty" or [I plead] not guilty" is "entering a plea".
Once the accused has entered a plea, the court case can take a different path depending on what the plea was.
In your example, Mr Wilson was asked in court effectively if he had committed the crime and he said that he had not. The court case will now continue with Mr Wilson pleading his innocence and it will, of course, be down to the prosecution to prove that he is lying and that he is, in fact, guilty.
I don't know if the wording is genuine, but in most TV shows, the judge says "To the charge of abduction of John Smith, do you plead guilty or not guilty?" and the accused replies "Guilty/not guilty, Your Honour".