If you are not a EU citizen, when you arrive at the airport you will first have to pass through passport or immigration control. Sometimes the queues can be quite long, so you should be prepared to wait. Keep your passport, visa and all other important documents ready to hand, for example:
Note down a telephone to International Students Office (+48 22 234 6039 for studies in Polish and 5091 for studies in English) in case of any questions from the side of the immigration officer. Once you have cleared immigration control, you can collect your baggage and proceed through customs to the arrivals lobby.
If you have a Mentor assigned, one should be waiting for you in the arrival lobby and help you to reach the University and/or your dormitory.
While staying in Poland you should carry with you all the time your Passport or Temporary Residence Card if you already have the permission.