Vaults are used to restrict access to items e.g. Cards, Boards, Kanbans, Lists, Documents & Media.
Every Lumi User has a Personal Vault, and you can create a Team Vault to limit the access to specific items to a group within your Lumi Project.
To create a new team vault, go to Vaults by pressing the shield icon in the column on the left and then press the plus
Give your Vault a name, then "Add".
This is your new Vault! You are the only one in here, as the owner, you can add some other users.
Press the plus button in the Vault heading and search for users in Lumi to add.
To remove a user from the Vault, press the bin icon next to their name.
You may want to change the owner of the Vault as they are responsible for adding and removing users. As the owner, you can edit the owner by pressing the pen icon next to your name, then the cross next to your name, search for another user and "Assign Owner".