Go to your account settings page.
On the right hand side you'll see the Profile column. Click on Upload and choose your profile image.
Click on Save changes at the bottom of the page.
You can also change your profile image by clicking the pencil button on the right side of your Profile. A pop-up window will appear and clicking on the camera button will allow you to upload a new profile image.
You must click 'Save changes' in the bottom right corner for your new profile image to be updated.
Note: If changes don’t apply, clear your cache and cookies in browser settings. File uploaded has to be JPG/JPEG, to avoid automatic resizing upload a custom photo at 500px x 500px resolution.