If the goods have a value less than $ 100 (and that they are non-commercial quantities), you may go to the customs office of your jurisdiction with the documents that certify you as an importer, so that they can prepare the Customs Declaration Form ex officio to carry out the formalities. For commercial merchandise or value greater than $ 100, you must contract a Customs Agent or Agency.

Art.136 General Customs Law (LGA) and 433 Regulations to the General Customs Law (RLGA).
You must present the product purchase invoice, the shipping document (air waybill, bill of lading or Bill Of lading). Also according to the type of product you must present the corresponding health permits (the agency helps you in this process). If the product you wish to import is subject to any tariff agreement, you must present the corresponding certificate.

We will be happy to advise you in the process.
Taxes are canceled according to the tariff classification of the product, a customs agent is the professional indicated to carry out this calculation.