To change your profile picture, click on the "Change photo" button in the profile menu. 

Browse the photo that you would like to upload from your computer with the "File upload" icon, or you can drag the picture you wish to upload. After uploading, you can to crop the picture. If you would like to save the pricture, click on the "Save" button. 

If you already have a profile picture uploaded, you can delete it by clicking on 'Delete image'.