Yes, you will be responsible for providing your own costume, and for wearing it the whole time you're on set.
The Chosen's team will send out a "Style Guide" that will specify what you can and should wear. Many people last time found items at thrift shops. To collaborate with other extras on costumes, feel free to head over the The Chosen Extras Facebook page: https://www.facebook.com/groups/745787122904466
PLEASE NOTE: This group was created by some who attended the Sermon on the Mount. While it is not maintained by Angel Studios or The Chosen, it can be a useful place for attendees to communicate with each other. We also try to keep an eye on it to see what common questions are popping up so we can resolve those for you!
You will be able to bring a bag to carry items in, but it must fit the style laid out in the Style Guide, and limit one bag per person.
Please note: EVERYONE who comes on set must be in costume, even if you are only accompanying a minor.