After opening the "Site Network Installation", make additions to .hdaccess and wp-config.php as instructed there.

The .hdaccess and .wp-config.php should be written during this process.

The .htaccess should be

<IfModule mod_rewrite.c></IfModule>.

Overwriting this is OK.

Re-login when done.

*Don't forget to restart XAMPP Apache after changing the .htaccess.