To set up discussion forums click on the "Forum" icon. Click on the "Add" button at the top right.
You can add as many forums as you like. Think of forums as rooms to discuss certain topics in. So for example you could setup the following:
Training - a forum to discuss training-based topics
Finances - a forum to discuss everything relating to finances such as invoices, fees etc
Events - a forum to discuss club events
General - a forum to discuss anything not covered above
And so on
Inside forums are "Topics". Anyone with the "View Forum" permission can create topics.
Inside topics are "Posts". Again, anyone with the "View Forum" permission can create posts.