CKEditor

To use the CKEditor with Upload function, add Rails-CKEditor to your Gemfile (gem 'ckeditor') and follow Rails-CKEditor installation instructions.

You can configure more options of CKEditor "config.js" file following the Api Documentation .

RailsAdmin.config do |config|
  config.model Team do
    edit do
      field :description, :ck_editor
    end
  end
end

Note that CKeditor won't appear in AJAX-loaded modals, due to CKeditor limitations with AJAX loading/unloading (basically it's crap).

More here