Simply download the SandBox Previewer, enter your username and password and preview the app you're making. For building and designing your own app, please use the SandBox mobile app builder (www.sandboxapp.io).
SandBox Commerce's previewer app allows you to demo your mobile retail app experience you built on their platform. There's no other company that allows you to build and deploy an entire mobile retail app in less than a day!!
Love the UI!