I hope you can allow yourself to go with an open mind, curiosity, and trust.
"Trust the process." my T tells me. Sometimes it's relieving to think that thought.

I don't think you are going to be asked to 'perform' or act out your anger. I imagine this is a kind of introduction to this room so you can become familiar with it.

This new experience can be like a good book where you look forward to see what will happen next!