How to set so guests can't post?

I set it so guests can post and that was a mistake. How do I set it back?

Click on your admin panel. Click on the 'General' tab. Under 'Forum', click on 'categories & forums'. That'll bring up all the sections of your forum. You'll have to click on each section and click on 'Permissions' and that'll let you change the permission for that section. You'll have to go through each section and change the permission for each one individually.

Yes it is but I'm not sure how to mark it solved.

To add the solved topic icon:
Press the edit button in the first message of a topic.
Check the green solved topic icon.
Press the send button.

Topic Solved & Locked