checkboxes and multiple values?

hello.

i need support for multiple checkbox values, let say an ability to select 2 out of 3 options.

as far as i understand the solution is here:
http://wordpress.org/support/topic/plugin-more-fields-patch-checkbox-morefields-multiple-values

but i dont know how to implement it,
any help would be appreciated.

http://wordpress.org/extend/plugins/more-fields/