You can easily bulk assign resources including Banners, Scripts, and Pixels to creatives within the Creative Manager. Open the campaign and multi-select the creatives.
Click Assign Resources button.
Select the Resources you would like to update (Banners, Scripts, Pixels).
Add your Resources.
Click X to close the Resource Panel and Save the Resources across your selected Creatives.
Note: Bulk Assigning will replace any existing Resources that were previously assigned in that Category (Banners, Scripts, Pixels)