how to submit test score after selecting university (immediately after test) but not selecting the department

https://preview.redd.it/omwlm6ujrine1.png?width=1055&format=png&auto=webp&s=aad5100095949321549909755b80601a7a0b5747

After the test concluded, I was told to select 4 universities of my choice. As i wasn't aware of the respective department codes, I was told to select the unis right now and choose the departments later on while sending the scores. But here's the question: how do i make changes in the department codes and send them? i am aware of paying extra fee and sending but what about selecting the department and sending the scores from the free list?