danechitoaie wants to do two quite different things:
- Close registration so that new members can only be created by admin fiat.
- Hide the forums completely, so that only a login box is displayed to unauthenticated users.
It is already possible to close registration. Admin creation of accounts will be added in the future, as I noted above. That takes care of the first bullet point.
The second one is a bit tougher. The login form is a modal dialog, so it would probably take an extension to display that dialog on a page other than the pages Flarum currently offers. Let's use this thread to discuss the possibility of creating such an extension.
... One simpler alternative might be to .htaccess password-protect the directory where Flarum is installed, and give your members a password that will allow them to see the site. They'd then use the "Log In" link to log in as usual.
Of course, that would mean giving members two passwords to deal with. If that's not an option, then it's probably going to need a bit more work.