Snapchat doesn't offer a native Apple Watch app, so full access isn’t possible, but you can still receive notifications by enabling them on your iPhone via Settings > Notifications > Snapchat, and then mirroring them to your Apple Watch through the Watch app > Notifications > Snapchat.
This lets you see alerts when someone sends you a Snap or message, though you can’t open or reply to them from the Watch.
While you can’t view or send Snaps directly, some users use workarounds like opening Snapchat on their iPhone and using the Watch as a remote shutter through automation or AssistiveTouch.
Additionally, third-party apps like WatchWeb attempt to load Snapchat through a mini browser on the Watch, but these are very limited and not secure.
Overall, Snapchat’s core features—like viewing Snaps, stories, Bitmoji, and using the camera—are not supported on Apple Watch.