In short: you can't.
The preview client that is available from the PureWeb Reality Console is a version of our React web client template. It has been customized to allow you a quick way to preview and test the streaming for your game packages; it is not intended for use as a production tool.
What this means is that the preview client cannot be modified. More specifically, the URL, branding, colours and layout of the page cannot be changed for any reason.
To take full advantage of the PureWeb Reality platform, including adding your own branding and colours, create and host a web client using our template.
Here are a few tips for customizing your web client: