Build from form has_many through

hello.
i would like to add to an existing project some future.
i work with redmine, i would like to create for each project a
check-list.
check-lists are managed by admin, so he can create , update and delete
tasks.
A check-list look like:
Commercial:
task-1
task-2
task-n
developper:
task-…

its just an example, admin can create other tasks and tasks-categroie.
this part is ok:
i have a model named ncchecklist:

class Nccheklist < ActiveRecord::Base
belongs_to :parent, class_name: “Nccheklist”
has_many :children, class_name: “Nccheklist”, foreign_key: :parent_id

def self.roots
return Nccheklist.where(parent_id: nil)
end

def siblings
if parent
parent.children.where.not(id: self.id)
else
Nccheklist.top_level.where.not(id: self.id)
end
end

def has_parent?
parent.present?
end

def is_leaf?
self.children.empty?
end

def is_root?
parent.nil?
end
def has_children?
children.exists?
end

end

now i would like to add a form in the project view with tasks and radio
button true/false, and user check it if he and the task.

each project have all tasks but of course with different value.
the goal is that each user ( employee ) say if yes or no he has end task
attached to his position.

hope some-one can help me and sorry for my poor english.