Hi!You should try through websites of english language schools directly-just browse the net in search of the phrase "szkoła języków obcych" and go to the section "praca" or "współpraca".On each website you will find a section in english explaining how to apply for a job in a particular institution.
You may be expected to take in some intensive course in grammar teaching first.
You may try in biggest well-known schools such as "Empik", "Berlitz","International House","Profi-Lingua","British Council".
You can also try to work as a freelance interpreter-in polish "tłumacz".In many places there is a preference for native speakers.Then you should use phrases"biuro tłumaczeń", "tłumaczenia" during browsing the net. As application forms in such places are often in polish you should try to contact your prospective employer directly through e-mail.
Good luck!!!