Hi Karina. It can be complicated until you get used to moving around the menus. No worries. You can also do this:
At the top of any screen, you will see your avatar image. Click on the little arrow next to it.
A menu box will appear. Click on "edit profile"
This is your profile page. You will see two menu bars at the top of the screen. Click on "avatar."
Upload a picture from your computer to use as your new avatar. If you need any help with that part, just let me know.