Hey, I saw that a lot of students were struggling with this class since Blender changed a lot of elements in Geometry Nodes. So sharing my settings in hopes it helps a lot of students complete their projects. Feel free to ask me questions.

 

Here is my Geometry Nodes setup. 

The big differences are that you have to use Object Info (with your instance object selected) and connect that to Instance on Points which will then be connected to Realize Instances.

 

And here are my modifier settings, feel free to customize them to your personal preferences.