First you have to load money to your account via online bank, credit card, or Paypal.
You can upload files to the service and release your prints from any Print in City device. There are no copy cards used, instead printing works with a personal pin code. In addition to Otaniemi, there are Print in City devices also in Helsinki.
Only pdf files can be uploaded to the service. Thus, all other formats must first be saved in pdf format before printing.