All finished videos and images land in the Library (sidebar icon). There you can browse by folder, filter by type (video clips, final video ads, static image ads), search, and download.
Single clips (UGC, UGC Hook, Product Animation, etc.) are saved under Library → Video Clips, not the main Library view.
If an asset was just generated it may still be processing, generation usually takes a few minutes. Wait a moment and refresh the page. If nothing arrives after ~15 minutes, check Settings → Credits for a refund entry (failed generations are refunded automatically) and see Failed generations and refunds.