Aurora: Set forum permissions
In the community, you can set forum-specific permissions to control who can read, start, reply to, and manage discussions.
At the community, category, group, and board levels, Aurora includes the...
Knowledge Base Article
Firstly - I believe the Grant forum-specific permissions to a role should describe the step of Choosing the Forum you want to have specific permissions for.
I had to paste this into a text editor to remove the HTML tagging that came from your own Post (the HTML restrictions wouldn't allow me to paste).
Would prefer to see the "Remove Formatting" button in this reply toolbar.