Checkbox in Form where taking value in models -> into DB

I have an admin form, and I would like to know how can grab the value in my models to puts in my form.ex = Checkbox1 = "cat", Checkbox2 = "dog". (and save that in DB when submitting)

Firstly I have had a new column in my Admin DB : t.string "admin_types"

Here my form admin :

    <div class="field">
      <label>Email :</label>
      <div class="<%=@admin.errors[:email].empty? ? 'field' : 'field error'%>">
        <%= f.email_field :email, autofocus: true  %>
      </div>
    </div><br>

    <div class="field">
      <label>Name :</label>
      <div class="<%=@admin.errors[:name].empty? ? 'field' : 'field error'%>">
        <%= f.text_field :name %>
      </div>
    </div><br>

    <div class="field">
      <label>Password :</label>
      <div class="<%=@admin.errors[:password].empty? ? 'field' : 'field error'%>">
        <%= f.password_field :password %>
      </div>
    </div><br>

    <!-- ACCOUNT TYPE ADMIN -->
  <label>Account Type?</label><br>
    <div class="inline fields">
     <div class="field">
       <div class="ui radio checkbox">
         <input type="radio" name="frequency" checked="checked">
         <label></label>
       </div>
     </div>
     <div class="field">
       <div class="ui radio checkbox">
         <input type="radio" name="frequency">
         <label>Admin</label>
       </div>
     </div>
    </div>

  <div class="inline fields">
   <div class="field">
     <div class="ui radio checkbox">
       <input type="radio" name="frequency">
       <label>User</label>
     </div>
   </div>
   <div class="field">
     <div class="ui radio checkbox">
       <input type="radio" name="frequency">
       <label>Moderator</label>
     </div>
   </div>
   </div><br>

And now my models admin:

class Admin < ApplicationRecord
  after_initialize :set_default_role, :if => :new_record?
  admin_types = [:admin, :user, :superuser, :moderator]

  def set_default_role
   self.admin_types ||= :user
  end
end 

When I create a user, it is automatically created with the role "user" ... everything is good on this side. On the other hand I would like to have some advice to know how registered the values of the form in database.

Thanks.