There are two ways you can upload and change your picture.
From your home page, you will click on the circle icon next to the notifications bell in the top right corner. Then click on 'My Profile' and you'll be taken right to your profile page.
You will see a pencil icon by the circle in the top left corner. By clicking on the pencil icon, you'll have the option to upload an image.
From your home page, click on the circle icon next to the notifications bell in the top right corner. Then click on 'Settings.'
You will be taken to your account settings page where there's a profile section. Within that section, click on the circle and upload your picture. You can change the picture at any time.