How to use "ot_get_option" in function.php ?

You can use the following code:

function cm_to_wp(){
	if(ot_get_option('cm_title'))update_option('blogname', ot_get_option('cm_title'));
	update_option('blogdescription', ot_get_option('cm_description'));
        // code ....
}
add_action('after_setup_theme', 'cm_to_wp', 2);

The ot_get_option() function is loaded during a hook and is not directly accessible from the functions.php file. Like Vincent demonstrated, you need to wrap your code in a function that is called from an action hook to avoid the error message.

Cheers,
Derek

Thanks Vincent and Derek.