This might be just what you are wanting to do but you don't use INSERT you use ALTER
Put a new field after another field
ALTER TABLE `tablename` ADD `newfield` VARCHAR( 10 ) NOT NULL AFTER `fieldname` ;
Put a new field at beginning of the table
ALTER TABLE `tablename` ADD `newfield` TINYINT( 2 ) NOT NULL FIRST ;
Put a new field at the end of the table
ALTER TABLE `tablename` ADD `newfield` VARCHAR( 7 ) NOT NULL ;
That should do what I believe you are asking about, as you can see if you were looking to insert then that might be why you could find the way to do it, unless you want to do something different.