Click the button (top right of the screen), "Turn editing on".
 
Click, "Add a resource..."
Add a resource
 
select, "Link to a file or website"
add a link
 
Give a name for this link. Click, "Choose or upload a file ..."
set up file
 
Click, "Upload a file "
upload
 
Click, "Choose" to choose the file you want to link.
choose a file
 

It will automatically return to the Link editting page, make sure the file name is beside "Location".

Click, "Save changes".

save changes
 
Click the Course name, e.g "Physiology", to return the course home page .
click course
 
Click the small icons at the right side of your link as you wish...
edit buttons
 
Click the "Turn editing off" to return to normal mode.
turn off editting
 

That's it. You are the master of your course now!

This only reveals a small portion of this platform, you can explore much more as you wish...Enjoy.