A PESEL number is an 11-digit personal identification number used in Poland. Not every student is required to have it. You need this if you register your temporary residence (meldunek/zameldowanie) and sometimes it is needed when opening a polish bank account. To get your PESEL number visit Centrum Usług Publicznych on 1 Colonel Witold Pilecki Street, 45-331 Opole, take the ticket from the machine, find the service desk (often indicated by the letter at the beginning of your number from ticket), and wait till your number will be displayed/called. To get the PESEL number take your passport and accommodation confirmation issued by dormitory administration (if you stay in dormitory). You will receive your PESEL number immediately.
While getting your PESEL number you can also ask to register your residence (meldunek/zameldowanie). To do this, do not take another ticket. Instead, after you will receive your PESEL ask the administrative staff at the desk if they can also register you in the system. Registration will be done immediately.