A SharePoint site comes with one default library, however you can create as many libraries as you need provided you have the right level of access (Edit and above). You can also add lists or other apps to your site.
Instructions
From your site's homepage, select +New from the menu bar.
Then chose what you want to add to your site and provide the details when prompted.
You can also complete these steps from the Site Contents page (select the Gear icon (top right corner)) > Site Contents.