In the cart, you will find the "notes" field where you can specify your invoice request. At the time of payment, in the checkout, you will find the additional fields "tax code" and "pec" (you can also enter the SDI code directly in the notes), moreover, you will find the space to indicate any billing address different from the shipping address.

Alternatively, you can write to sending all your data. Remember that, according to Italian tax legislation, it is not permitted to issue an invoice beyond the twelfth day from the date of purchase.