When contacts get to a certain step of your campaigns scenario, you can send a focus item to them.
You need first to create a focus item.
To send focus item to contacts, it will go through the campaign action "Show focus item".
But this action is only available after the decision "visits a page". You won't find this action if you did not add this decision before.
So in your scenario, contacts must visit pages to see the focus item.
So add the action "Show focus item" in the positive branch.
Contacts that visit the page (related to the decision) will see the focus item directly.
You do not need to place the focus item script in the page of your website. The action "Show focus item" will automatically send the script to the page to display the focus.