You can upload your profile picture at any time.
First, open the dropdown menu in the top right corner and click on Profile Settings.
Once on your Profile settings page, click on your existing profile picture:
Select a picture from your Desktop to upload a new profile picture. Note that the picture will be cropped to a square upon save. Use the zoom in and out slider and the drag functionality in the picture frame to fit your picture as you wish it. Click the Save button to save your picture: