The Find My Device on Xpeira Z3 is your saving angel in case you lose your phone, as you can locate, lock or even erase the data on your Xperia Z3 remotely. To setup Find My Device on Xperia Z3, do as follows:
1. Make sure you have already added your Sony account to your Xperia Z3 (To learn more, read: How to Add a Sony Entertainment Network Account on Xperia Z3)
2. Open Settings and under the Personal settings, go to the Security settings
3. Under the Find My Device settings, tap the my Xperia option
4. Use the slider button and Turn on my Xperia.
5. Read the Terms & Conditions and accept it (You may be asked to confirm the Google's Location Services warning)
6. my Xperia is activated.
Now, you just need a browser, head to the my Xperia page, login with your SEN account and enjoy the benefits of Find My Device on Xperia Z3.