This is the 2307th most frequent Polish word.
ustalić
To determine, establish, or set.
Here, 'ustalić' is used in the sense of determining or setting a specific time or date.
Musimy ustalić termin naszego spotkania.
We need to set a date for our meeting.
'Ustalić' here means to figure out or establish facts related to an event.
Policja próbuje ustalić, co się stało.
The police are trying to determine what happened.
In this context, 'ustalić' means to obtain or find specific information.