Campaigns are for marketing purposes, and this is where leads live. To see, set up, or edit your campaigns or anything related, please go to the pane on the left, click Settings, and click Marketing.

Settings > Marketing

Here you can see who has access to the leads, the actual campaigns, and the source of the leads.

Under Campaign Teams, you will see the personnel with access to the leads. Click the Campaigns tab to see, edit, or delete a campaign. Lead Sources will display from where the leads were obtained.

To make additions under any of the tabs, you can just click the "+" which is typically on the right close to the search field.