The Help Center provides guides for Schoology users in each of their respective categories:
By moving through the articles in the guides from top to bottom, you'll get a good sense of the features available to you on Schoology.
The Schoology FAQ's and System Requirements & Troubleshooting Tips areas also house tips that are useful for both new and veteran Schoology users. If you're looking for new things to learn about in Schoology, these areas are a great place to begin looking.
On another note, if you'd like to ask a question to the Schoology Community, or share a suggestion about the platform, you'll find a list of Q&A and Feature Requests forums in the Community.