Hello Maria!
If your university is a partner university of Saxion, in order to partake in a semester abroad, you will most likely need to be nominated by your own university so you can sign up. Thus, I would advice you to contact the international office of your university as quickly as possible, as administration periods are often limited and I do not know how your university (Vistula University) handles them specifically.
As mentioned, the organisation of the semester lies with your home university, but if you have any questions about studying at Saxion, feel free to reach out again or contact the international office (internationaloffice@saxion.nl ).