There are two different ways to set up a new session in BigBlueButton:
You can create a BigBlueButton session in form of a learning activity in an existing Moodle classroom by using the according interface (link). You do not require further access rights to use BigBlueButton in Moodle if you hold the teacher role in the Moodle classroom.
You can also use BigBlueButton independently from Moodle on this page: https://bbb.uni-due.de/b. In this case, you require access rights in order to set up new sessions in the first place. For this purpose, please send an e-mail to firstname.lastname@example.org stating your university username. Access will be granted to you as soon as possible, i.e. it will be subsequently reported to you by e-mail.