Just go to: WebUntis.com and login for the first time with your individual access data.
After logging in with your user name and password you will see a button on your start screen which always brings you directly to the next step you need to do in order to create a timetable. When you log in for the first time this is the first step of the data entry wizard (to create a school year). The data entry wizard guides you through all necessary data entries up until timetable planning.