The Line Item level represents a campaign that will run under an Advertiser. To create a new campaign, open the Advertiser menu by clicking on the name of the Advertiser in the Advertiser tab, and select ‘New Line’. See the following page for details on setting up a Line Item: Setting up a Line Item.
If you do not see the Line Item that you are looking for here, try switching the ‘Filter Status’ to ‘Inactive’. If the Line Item appears under ‘Inactive’ and you would like to re-activate it, click on the Line Item name to open the Line Item Settings. Select ‘Edit’, then check the ‘Active’ box. For more on the ‘Active’ box see here: Active Box.
For additional information on the metrics for the Line Item displayed here see the following page: Line Item Level Metrics.