You will need to grant Chrome or the Snapchat app permission to use your Chromebook's camera and microphone to send snaps or make calls.
This is the best way to get the full app experience, including filters and camera features, provided your Chromebook supports Android apps. how to get snapchat on a chromebook
Once downloaded, find Snapchat in your app launcher, open it, and sign in with your credentials. You will need to grant Chrome or the
