Hi there;
I use setup-nextcloud.php install sucefully , but it show following :
Because the .htaccess file is not working, your data directories and files can be accessed from the Internet.
See the documentation for how to configure the server properly.
I don’t really know why , and I did’t find do something on ,htacess . Looking forward to help.
Bless you
as you’re not really providing any information on your setup, server, envorinment, etc all i can do is reminding you of the search function of this forum - marked by a 
(upper right corner) -
you can be sure to find some dozen threads dealing with .htaccess and how to set it correctly
have fun