The users have register and login before download something from my forum. How to set this?
There is some information in my forum which is very useful, but people could download it for free without even registering. How should I set up this?
First, you should decide whether the forum and topic should be accessible for Guests or not. If they should have an access to read the content, but they should not be able to download the content, then you should go to Dashboard > Forums > Forum Accesses Tab, edit the "Read Only" access and disable the "Can view attached files" permission.