Snapchat is available for Android and iOS.
Snapchat for Android
Snapchat for iOS

Download the app, open it, then select "SIGN UP".
Once setup, tap the ghost at the top, then tap "Add Friends", then "Add by Username", the type "Chelmsfordbeer".

Alternatively, simply point your Snapchat camera at the image below, and then press and hold on the screen.