update database with checkboxes - rails

So I have a users model which is associated to activities and activities are associated to a completed model?.

What I am trying to do is update if an activity is completed when a checkbox is clicked.

Here is my view:

  <% @user.completeds.each do |task| %>
    <tr>
      <td><%= task.activity.name %></td>
      <td><%= task.activity.type.name %></td>
      <td><%= task.activity.points %></td>

      <td><%= check_box_tag 'finished', '1', task.finished %></td>
    </tr>
<% end %>

This all works great and shows if an activity is "finished" but I am having a hard time figuring out how to update the database with the checkbox. While I would like it to update when you click the checkbox I am ok with having a save button to save them all at once. Which ever would be easier probably would be best for me as I am just learning rails.

Thank you for any help.