If I lost my Apple Watch how do I find it if its dead

Hi

The following support article explains your options in the event of your Apple Watch being lost:

If your Apple Watch is lost or stolen - Apple Support

If the watch battery is fully discharged, then the Apple Watch can only be found by physically looking for it.

The old fashioned way - look for it. Otherwise, it's gone.

How do you lose an Apple Watch then forget to find it?

So enable lost mode on the Apple Watch on the find my iPhone app so that other people can't activate it without entering your passcode.

Enabling Lost Mode is covered within the support article linked in my previous reply (within the section headed "Put your Apple Watch in Lost Mode").