How do I view plans that have been shared with me by another teacher?
Here, click the "Class" drop-down in the upper-left and scroll down to locate those shared classes. Click on a class to view those plans.
If your colleague has allowed the copying or linking of their plans, you can follow the steps here to copy or link those into your account - https://planbook.uservoice.com/knowledgebase/articles/1947163-copying-linking-lessons-from-others