Go to Ad mediation section
After you are under Ad mediation, find the campaign you want to import creative in and click on the +Add creative button.
If there is no campaign in the list click on +Add campaign button and add your campaign first. How to add a new campaign.
In the next form choose ad network name you want to import creative. Click on 'Ad networks' dropdown list and you will see the full list of linked ad networks:
Select an ad network and you will see an import button (if ad network allows auto-import):
Click on it and you will see the full creatives list for the selected network:
Choose one creative and click Next. All fields will be filled automatically.
That's it, scroll down the page and click on the Save button:
If Ad Network doesn't support auto-import you will be notified about it:
No worries. You may just import creative manually. You will have to go to the ad network panel, find your ad zone and its ID and copy/paste them into the form fields.
How to find ad zone code/link url and zone_id read in Ad networks manuals
Direct advertiser or partner network
If you sell traffic to a direct advertiser or another partner network, leave the ‘Ad Network’ and ‘Zone ID’ fields empty. Fill in ‘Code’ or ‘Link URL’ fields manually and add your fix CPM in "Flat rate".