Navigate to 'Campaigns' and click on 'Add campaign'.

Create a campaign name, add a tag (optional) and set the status to 'New'. Then set the preferred lead time (date) by clicking on the calendar icon. Click on 'Save'.

Now the campaign is in the overview of campaigns.

You may also want to edit an existing campaign.
First click on the campaign which you want to edit and then click on the pencil icon of that campaign.

Edit the campaign name, tag, status and or lead time. Confirm your changes by clicking on the 'Save' button.