Go TO And Replace (MySql)

I have table it's name Members contain this field (ID,username,age,password)

How can I go to the recode that it's ID=4 and replace the (username,age,password) with other values

Thanks

like the SQL statement?

$theSQLstatement="UPDATE Members SET username="whatever", age=\"$whatever\", password=\"$passwordInfo\" WHERE ID = '$theIDtoUpdate'"

then run it through a mysql_query

mysql_query($theSQLstatment);

this is of course after you've logged in and established a connection with the mysql database.