Your instructor may use a Live Classroom component to teach all or part of your class using Class for Web (formerly Collaborate):

Live Classroom is an online classroom experience offers real-time video conferencing with interactive features, such as audio, video, an interactive whiteboard, application sharing, breakout rooms, and chat.
If your instructor is using Live Classroom, they will place a direct link on the course menu.
You will not need to download any software.
Learn more about using Class for Web (formerly Collaborate):
Ask your instructor if you have questions about using Live Classroom in a specific course.
Your instructor may choose to record Live Classroom sessions for students to view later.
If this is enabled for your class, go to Live Classroom and click on Recordings to see a list of all available recordings for your course:

When you open a recording, it will launch in a player with playback controls; this will look the same as your Class Collaborate session.
If your instructor has enabled it, you may be able to download the recording, chat transcript, and/or caption transcript. Open the Recordings menu to access the download options.
Give yourself time to learn what you can and can't do in the session. Start with the basics: add a profile picture and set up your audio and video. If you are presenting, make sure you can share content. Practice using the tools.
If you can't be early, at least be on time. Let your instructor know if you're going to be late or absent. Everyone can set notifications to alert them when someone has joined the session and may see who is joining when.
Don't assume everyone automatically recognizes your voice. State your name the first few times you speak. Give everyone a chance to know you.
If you are sharing video, look at the camera and not the session. It may feel weird but it shows you are engaged in the session. If you need to multi-task during the session, shut your video off to avoid looking distracted.
Nothing is more distracting than background noise, such as the sound of typing or a private conversation. It can give the impression that you aren't paying attention. Learn how to turn your audio on and off.
You may be joining the session from somewhere private, like your home, but you are not alone. You are face-to-face with your peers and instructors. Make a good impression. Participate. Don't talk over someone. Raise your hand if there is no opening to speak. Type questions and feedback in the chat. Pick your best profile picture. Watch your mannerisms and facial expressions.