The 'Build Content' button is located near the top of your 'Course Area'. This tip deals with the difference between the first two links in 'Create': 'Item' and 'File'. Essentially, you create an 'Item' if you would like the flexibility to create a list of links or attachments, add images and notes, etc. Creating a 'File', on the other hand, only uploads ONE file at a time, such as a pdf of one of the Lecture Notes in a series, and is used if you want to release the contents on a specific dates.
This is how the pages appear when you use 'Item' vs. 'File'.