You're working on a Display & Video 360 campaign and want to change the end date for multiple line items. You decide to make bulk edits using structured data files (SDFs). What should be your first step?

To make bulk edits to line items using structured data files (SDFs) in Display & Video 360, the essential first step is to download an existing SDF. This downloaded file serves as a template containing your current campaign's configuration, including all the line items you wish to modify. You then edit this downloaded file offline to change the end dates. "Make changes to the SDF in Display & Video 360" is incorrect because SDFs are edited externally, not directly within the DV360 interface. "Upload the updated SDF to Display & Video 360" is a subsequent step, occurring only after you've downloaded and modified the file. "Make changes within the Display & Video 360 account" describes manual, individual edits, not the bulk editing process using SDFs.