Open it

Unzip the download and open Christmas_Gift_Boxes.blend. All 25 boxes are in the Christmas Gift Boxes collection.

Use it from the Asset Browser

1. Put Christmas_Gift_Boxes.blend in a folder you like.
2. Blender → Edit → Preferences → File Paths → Asset Libraries → add that folder.
3. Open the Asset Browser, pick the library, and drag boxes into your scene.

Or append them

File → Append → Christmas_Gift_Boxes.blend → Object (or Collection) and pick the boxes you want.