Use htpasswd to create password file, or add password
htpasswd -c .htpasswd fred
htpasswd .htpasswd linda
Then create a .htaccess file with the following text (not the path to the password file has to be full path)
AuthUserFile /full/path/to/.htpasswd
AuthType Basic
AuthName "My Secret Page"
Require valid-user
To protect individual files, use
AuthUserFile /full/path/to/.htpasswd
AuthType Basic
AuthName "My Secret Page"
<Files "mypage.html">
Require valid-user
</Files>
<Files "myotherpage.html">
Require valid-user
</Files>