Hey!
Here’s an artcicle about password protected pages - https://support.wix.com/en/article/wix-editor-password-protecting-a-specific-page-of-your-site
As far as I know, there’s currently not the ability to have someone put in the password and be able to access all the pages. That being said, it might be possible to build something with Velo, and to store a session token that allows them access to all the pages (using code). I’d recommend asking the Velo forum if you plan on exploring that method