Looking for Apple Watch fall app

You turn it on in settings, it's not a separate app:

https://support.apple.com/en-us/HT208944

It's called fall detection;

Open Settings on your iPhone, then tap Health/Medical ID and check your details.

Then;

Open the Health app and tap the Summary tab.

Tap your profile picture in the top right-hand corner.

Tap Health Profile, then tap Edit.

Check your information, like height, weight and age.

Tap Done.

And in the Watch App tap on emergency sos and tap on fall detection to turn it off or on.

If you're over 65 then fall detection is turned on by default.