How to set a watermark camera for mobile phones?

Take OPPO R9S mobile phone as an example, the setting method is as follows:

First, find the "Settings" icon on the phone desktop, and click Enter. ?

2. After entering the phone setting interface, find "Camera" in the menu bar and click Enter. ?

Third, after entering, find the "photo watermark" and turn on the switch in its column, thus setting up the watermark camera.