Learn how to enable and use the handoff feature on your Apple Watch. Handoff allows you to resume what you were doing on your Apple Watch when you switch to the paired iPhone. You can, for example, read a message on your Apple Watch and then reply it on your iPhone, or simply accept a phone call using your watch and then resume it on your smartphone, the applications of the Handoff feature are various. All the apps that support this feature will appear at the lower left corner of the iPhone lock screen.
You can enable the Handoff feature in the Apple Watch app installed on the companion iPhone:
Open the Apple Watch app. Go to My Watch > General. Toggle the Enable Handoff switch on and that's it.