See details about how to get the $50 credit: https://canvas.wisc.edu/courses/272598/discussion_topics/1079256.
Then follow these instructions to create an account and redeem the credit.
Follow these instructions to configure the firewall to unblock all ports.
You already have an idea of what a shell is: you've been either using PowerShell (Windows) or bash (default on Mac) in CS 220/301. ssh stands for "secure shell", and it's a special shell that lets you remotely connect to other computers over the network and run commands there. An ssh key is like a randomly generated password that ssh automatically uses to access other machines (you won't generally type it).
Macs and recent Windows computers (Windows 10 with recent updates) should have a program OpenSSH installed, which will be the most convenient way to access your virtual machine.
Try these directions to create an SSH key and connect it with your cloud account. If it doesn't work (e.g., because you don't have OpenSSH), don't worry too much -- there are workarounds later.
Now it's time to actually create your virtual machine! Follow these steps.
If you were able to configure the SSH key properly in Step 3, follow these directions.
If you couldn't configure the SSH key, follow these directions instead.
Now lets get Jupyter and some other software installed. Follow these directions.