GlassFrog currently has two ways to add an image to your profile.
Option 1: If you have not linked your GlassFrog account to your Google account, then you will need to upload a picture of your own. Navigate to your profile page by clicking on your username. See screenshot.
Option 2: Link your GlassFrog account to your Google GMail account on the sign in screen by logging in with Google Sign-in. This will signal GlassFrog to being using your Google+ profile image. Note: This may require you to sign out by clicking "Sign out" on the top right menu. Sign in page: https://app.glassfrog.com/session/new