If you are running ads in Audience Network or in Instream Videos you can block your ads from running on specific websites or apps within the Audience Network or in the Instream Videos of specific publishers by uploading block lists to Facebook. Note that blocklists will limit your campaign’s delivery options and will result in fewer people seeing your ad. Use block lists to block your ads from running alongside certain types of content within Audience Network and Instream Videos.
How can I create a block list?
How can I use a block list in Smartly.io?
Once you have created a block list in Facebook you can use it in Smartly.io under Audience Network exclusions under Audience tab.