Quoting MARIMUTHU Ilayaraja:
> I am trying to add a custom field and give access to only certain
> people, for example release managers. But I think, there is no option
> in bugzilla to configure this function.
>


You can edit Bugzilla/Bug.pm, look for sub check_can_change_field, then
look for user->in_group('editbugs', and add this as a new if statement
AFTER that:

if ($field eq 'cf_mycustomfield') {
return 1 if $user->in_group('someReleaseManagerGroup');
$$PrivilegesRequired = 3;
return 0;
}



> And, Can I add a checkbox as custom field?


There is no support for adding a custom field as a checkbox.