Version 2.104 and up
This is a very easy task if you know how to work with Lightning page layouts. Open the page editor by clicking on the Edit Page link:
Then drag the CampaignItemRelatedList Custom Component to where you like to position it. In this example we have added it to be a tab called: Campaign Item List. But you can position it anywhere else on your page.
Click on save an return to your page. Configure your 8.5.4 Settings for the Custom Campaign Item Related List here.