Building your 3D and VR worlds works in the browser app. For this, you don’t need to install anything. Just go to https://studio.cospaces.io/ and get started. You should, however, use a desktop or laptop computer with the newest version of Firefox, Google Chrome or Safari to create your VR experiences.
If you want to experience your own creations in 360° or VR mode, you will need to install the CoSpaces app on your smartphone. You can download it for free on Android and iOS.