No software is out there that automatically creates a Forum for you, but there are free open-source forums/portals out there like CMS Forum:
http://www.cms-forum.org/
Also, some web site hosts, such as Godaddy, can "turn one on" (a forum that is) for you. This might be a better way for you to go since you're just starting out with this.
Setting up the forum on your own would take some degree of technical knowledge as you have to tie an application to a database.