Depending on how you want to structure your application, you can use configs files to update:

1. Global Settings
  ```
  # config/initializers/active_admin.rb
  ActiveAdmin.setup do
    config.css_classes = YAML.load_file(Rails.root.join("config/adminterface/css_classes.yml").to_s)
    config.components = YAML.load_file(Rails.root.join("config/adminterface/components.yml").to_s)
  end
  ```

2. Namespace Settings
  ```
  # config/initializers/active_admin.rb
  ActiveAdmin.setup do
    config.namespace :site_1 do |site|
      config.css_classes = YAML.load_file(Rails.root.join("config/adminterface/site_1/css_classes.yml").to_s)
      config.components = YAML.load_file(Rails.root.join("config/adminterface/site_1/components.yml").to_s)
    end
  end
  ```

3. Resource Settings
  ```
  # app/admin/users.rb
  ActiveAdmin.register User do
    config.css_classes = YAML.load_file(Rails.root.join("config/adminterface/admin/users/css_classes.yml").to_s)
    config.components = YAML.load_file(Rails.root.join("config/adminterface/admin/users/components.yml").to_s)
  end
  ```

4. For guides, please visit https://github.com/CMDBrew/adminterface