You can take a look of my attached screenshot below how to enabled mini registration form on your homepage.

Then you have to configure which custom field you would like to display on the mini registration form, but not all the custom field can able to display on mini registration.

Currently we only allow following fields to display on mini registration form.

				'joomla_username',

				'joomla_fullname',

				'joomla_email',

				'joomla_password',

				'birthday',

				'gender',

				'recaptcha',

				'address',

				'checkbox',

				'acymailing',

				'terms',

				'textbox'