bbPress
Forums in WordPress are also possible through plugins such as bbPress. If you want to install this you first need to log into WordPress itself and then you can go to the plugins page. Look for bbPress and click on install and activate.
After you have installed it click on activate and refresh the page with F5. Then you can click on the side of the page on forums and then on add new.
Set and fill this to your liking and when done click on Publish.
After this your forum will look like this: