Hey there, nikisuzamy.
Welcome to the Apple Support Communities! Thanks for posting about wanting some assistance with using the Find My app on your Mac. We'd be glad to see how we can help you out.
Based on the post you made, it looks like you're using a Mac that's running macOS 10.15, which already includes the Find My app on installation. Locate a device in Find My on Mac by following the steps here. You also used an example of your Apple Watch not showing up when searching on the iCloud website. If it's paired with your iPhone and that iPhone has Find My turned on, it is automatically on for your Apple Watch. Is that paired iPhone set up with Find My in Settings > Your Name > Find My > Find My iPhone?
Take care.