Remotely Ring, Lock or Erase Lost Mobile Data Online

If you have lost your mobile phone, then follow steps to find it by using Android Device Manager to remotely ring, lock or erase that device. Android Device Manager won't work for devices that are turned off, or that don't have a Wi-Fi connection or mobile data connection with an active SIM card.

First you need to Login Android Device Manager Account

After open account select your device & choose option : Ring, Lock & Erase

Ring

• Select Lock
• Type message in the Recovery message (optional) field
• Select Lock
• A button to call the number you typed will show on the phone's lock screen Online

Lock

• Select Lock
• Type password & confirm password 
• Select Lock
• Your current lock screen will be replaced with a password lock.

Erase
This option performs a factory reset on your device. Your apps, photos, music and settings will be deleted. After erase the device Android Device Manager will no longer work. It may not be able to wipe the content of the SD card in your device.
If your device is offline, it will perform the factory reset as soon as it goes online.

You can also Add a phone number & message on your Lost Mobile Screen Online