To change your profile picture, first visit your profile page. You can do this by clicking on your profile icon on the top right side of the home page. Once you have opened that page, you will find a menu on the left, below your profile picture. There, select Edit My Profile. You will see the option to Edit My Photo. Select that, and then you will have the ability to choose a new photo and to edit your thumbnail. After that, simply select Save Photo.