Create a new class and share the room code with your students. The room code is a different, random code each time you start a new room. Note that the room code is only valid for the active session, so you cannot reuse the same room code or share the code before the session begins, as the room is only active while you as a teacher keeps the room open.
Premium subscriptions include a permanent room URL, which can be customised to your liking. The permanent room stays open, and does not expire after 2 hours of inactivity (like the temporary room). Using permanent rooms, you can keep the same link to your room during the whole semester, and you can empty all students out of the room between classes.