If you're on the app, then click your profile pic on the top/bottom right corner of your screen(depending on the type of phone you're using). Then, click on the settings button on the top right of the profile background thingy, and after the screen loads, click on the 'Profile and Account Setting'. Once you've done that, a screen will load with the options to change your profile pic and stuff.
If you're on PC/website, your current profile pic will be displayed on the top right corner of the screen. Click on it and a list(i think) will appear below it. Press on the 'My Profile' button and once the page loads, click on the Settings icon next to the Coins Balance thing. After you do that, you'll be able to change your profile pic, background image, location, etc.
Hope this helps ig