Go to a course in myCourses and then select the Course Materials Tab.
Select Add Content from the Course Masterials Tab toolbar at the top left.
Under the heading Create an Item, select File.
Click the Browse button on the left side of the screen. (See figure to the right)
Navigate to the file you want to upload, and click Open. This should fill in the text box with the name of your file from your computer. If you do not specifiy a name, it will keep the original filename when it is uploaded.