And one more questions. How can i place checked checkbox for default options?

Let's suppose the field name of the checkbox is "newsletter".
Open web/codelib/df.fl.(tablename).inc.php and find the following array.

'newsletter'=>array(
XA_CLASS=>'CVCheckBox',
....................
....................
....................
....................
),

Insert this line to the array.

XA_INIT_VALUE=>array( 'reg'=>'Y' ),

The result should look like

'newsletter'=>array(
XA_CLASS=>'CVCheckBox',
XA_INIT_VALUE=>array( 'reg'=>'Y' ),
....................
....................
....................
....................
),