If you want to change your profile picture you just need to click in the cogwheel on the top left side of your screen:
Inside, you will see a settings tab for your account. There, you just need to press the button "change" and select an image you have in your device to set as your profile picture in the game 😊:
Pictures are usually approved in less then a day.
If you see an exclamation mark nearby your profile picture that means you did not yet check your Ball Collections. Once you view said Collections it goes away. 😉
Bare in mind, offensive images will result in account suspension or permanent ban
Good luck on the golf course and have fun! 😄