Usually for me the people just meet at the place, pull out their texts and perform them. They’re randomly picked unless there’s a paper with names on them. If you’re joining a musical they probably also want to test your singing and will give you a text for that as well
For auditioning it’s important not to be too tense and have your face glued to the script. Idk how much time you’ve got to learn it but it’s good if you look up every so often and act out. Talk slowly and make facial expressions. In the end it’s just a mix of voice acting, moving, and your face so try and mix all three together