An important consideration when working with Office 365 is to understand the difference between working in the "cloud" vs. using desktop (or client) applications.
When working online or "in the cloud" you can access all of the Office 365 Applications such as Word, PowerPoint, and Excel. However, cloud-based applications do have their limitations. You will not find all the "bells and whistles" in the online version of the App but you can do quite a bit. If you find you are missing features, you will need to move to the desktop version of the application. You will still be saving your files to One Drive but working on them from the desktop application
Video: Switching between Online and Desktop Applications