To apply for an international patent (PCT), the applicant must submit a single application in one four languages (Polish, English, German, or French) if the applicant chooses the European Patent Office as the International Searching Authority, or in Polish or English if the applicant chooses the Visegrad Patent Institute as the International Searching Authority. The application should be filed with one of the so-called receiving offices, i.e. the local patent office (in Poland it is the Patent Office of the Republic of Poland).
It is then forwarded to the International Bureau and to the International Searching Authority and is subjected to an international state-of-the-art search. The international search report is published and forwarded to the national offices of those countries in which the applicant has applied for protection. From then on, the proceedings are conducted according to standard rules adopted by a given country.
See -> What is the International Patent Application Procedure (PCT)?