This is separate from Amazon Ads. You'll go through it solo (or with your manager) — it's an internal/private developer app.
Steps (1–2 days for app approval):
- In Seller Central → Apps & Services → Develop Apps
- Register as a developer (one-time, takes a few minutes to submit)
- Add new app client: App Type = Private (internal use), Roles = Orders
- Wait for approval. Once approved, in the app card copy LWA Client ID + Client Secret
- Click Authorize → Self-authorize → click through → copy the refresh token
- Paste all 3 below.
Marketplace ID is pre-filled for the US (ATVPDKIKX0DER). Region defaults to NA.