There's currently no method of uploading or changing a profile picture in the app. Previously, if you signed in via Facebook, it would use your Facebook profile picture as the image.
We recently updated our account registration process to provide a more secure experience for our users. As a result, Facebook-connected accounts are no longer supported. New app users will be required to register using email sign up, and users that have previously registered with Facebook will be prompted to convert their profile into an email account.
If you would like the ability to add a profile picture in the future, feel free to send us an email at firstname.lastname@example.org. Your feature request will then be shared with our product development team for review!