When you have finished giving evidence
When the Magistrate or Judge says "You are excused", this means that you have finished giving your evidence. This means that you can go home or you may be able to sit in the back of the courtroom and listen to other witnesses but check with the prosecutor first.
Even when you have finished giving evidence you still need to check with the police prosecutor or the Witness Assistance Service Officer or ODPP lawyer about whether you can talk about court. Sometimes you may have to wait until all the legal proceedings have finished before talking about your evidence with friends, family or other witnesses.