Overview
You will need to
Identify the placements using Tag IDs
Target those placements
Identify the placements' Tag IDs
The Tag ID serves to identify specific placements within publishers. Whether your campaigns run on App and/or Web inventory you will be able to target Tag IDs when the information comes as part of the bid stream.
If you have a list of Tag IDs from your past campaigns on other platforms, you can use it.
If you want to check the Tag IDs from your existing campaigns (with performance information), you can check them using Reports and the Tag ID drill-down variable.
Create a Publisher list with them
Go to the Publishers list section and click on 'New Publisher list', a dialog will appear requesting the relevant information:
Add a Name for the new publisher list
Upload a file containing the TagIDs identifiying the placements
Click on 'Create' to generate the Publisher list
More info about the Publishers list section.
Target the Publishers list
Once the system generates it, to use it, you will need to select it on the drop-down menu of the Publisher targeting section on the campaign you want to use it.
Recommendation
If you intend to retarget specific placements from a live campaign, we recommend you to switch ON the target 'only inventory with Tag IDs' toggle within the Publishers section on Targeting.
This serves to ensure all the inventory your campaign is buying comes with TagIDs that you can later use.