If you want to view the file and see how it was made, or edit it, you need the authoring tool.
Many people already have VLC installed, and while it isn't a perfect Flash emulator, it can handle basic SWF files. swf+player+flash+file+viewer+best
Because Adobe removed the official download, the "best" player is subjective. Here is the deep, honest ranking: If you want to view the file and
Tier 1 (The Preservationist's Choice): Ruffle Tier 2 (The Purist's Fallback): Clean Flash Player
Tier 2 (The Purist's Fallback): Clean Flash Player Projectors
Tier 3 (The Pragmatist's Tool): SWF to Video/HTML5 Converters
Tier 4 (The Fool's Gold): Browser Extensions / NPAPI Plugins