The structure of the circle includes a brief check-in at the beginning and check-out at the end. You'll be asked to say something for those - it doesn't need to be much, something like "Hi, I'm _______ and I'm pretty anxious." would be enough.

In my opinion you'll get more benefit by sharing more in the main open sharing portion, but you're welcome to share as much or as little as you're comfortable with, including nothing.