1. Visit https://app.deckzero.com and click on 'Create'

If you are not already signed in, a prompt window will appear for you to Sign-up or Login
2. You will then have two options:

Add a Blank deck with all default settings: click to create a blank deck with Visibility Status set to 'Private Link Only', and Access setting as followings:

For how to change the default setting, check Change Configuration of a Deck
Add a -Multi-deck Topic with configurable properties: You will be prompt a window to create a Topic (deck folder), where you can specify the Topic name, front cover, visibility status and access permission.

For how to set up a New Topic, check out Create a New Topic