If you have lost your Android phone, and are struggling to locate it, you can just open a Google search box, and type in "find my phone". If the phone is nearby, Google can ring it for you. If it is far away, Google can locate it on the map for you. You just have to make sure that the latest version of the Google App is installed on your phone.
While Google always had Android Device Manager to locate lost phones, the latest initiative by Google is more user friendly. If you are on Chrome, you can even say the words, "Find my phone" as Chrome accepts voice commands.
However, this feature does not allow you to lock or erase your device. You can use Android Device Manager to do that.