To insert data into any table using yii migration. You can use insert method of CDbMigration class.
For example, I have table called user in DB which have 3 fields including email, username and password. Now, we want to have some user for testing, you can write down in up() method of Yii migration like following:
 class m130726_010519_insert_user extends CDbMigration
{
 public function up()
 { 
  $this->insert('tbl_user',array(
         'email'=>'test1@notanaddress.com',
         'username' =>'User One',
         'password' => md5('test1'),
  ));
  $this->insert('tbl_user',array(
    'email'=>'test2@notanaddress.com',
    'username' =>'User Two',
    'password' => md5('test2'),
  ));
 }

 public function down()
 {
  echo "m130726_010519_insert_user does not support migration down.\n";
  return false;
 }


}