I recommend creating a new calendar first (as shown in the picture below). In that case if something goes wrong, you can easily delete it.
Open the „calendar“ application → in the application, pick „calendars“ → next pick edit →
creat new calendar (in my case ročník 1; Kruh 1)→
Then go to the website browser → fill in the address www.trimed.cz→ click on „timetables“ → pick your year → your group → under the calendar you will find the link for your calendar →
click on that → in few seconds it will show you the list of events in the application→
add events to relevant calendar→ done!