I assume you are making a admin area, and this is a setting that determines whether someone from any country can be accepted or from some countries not.
You retrieve the values and save them in the database:
// Retrieving the form values, and cleaning them from HTML and quotes
$accept_all_citizenship = htmlentities(mysql_real_escape_string($_POST['accept_all_citizenship']));
$ud_not_citizenship = htmlentities(mysql_real_escape_string($_POST['ud_not_citizenship']));
// Updating the table
$query = "UPDATE settings SET accept_all_citizenship='".$accept_all_citizenship."', ud_not_citizenship='".$ud_not_citizenship."'";
$result = mysql_query($query);
mysql_query($query);
And then you retrieve its value on the page which has the form for people that want to apply, and check whether the citizenship is accepted. If you do not know how to do this, I strongly recommend you to read a bit more books on MySQL and PHP.
~G