Turn editing on.
On the left, under any existing blocks, is the "Add a block" menu.
Select the block you would like to add from the menu (if you do not see the block you want to add here, it may already be on your course page! Some blocks can only be added once to a course).
Once the block has been added it will appear on the left at the bottom. From here you can move (drag and drop) the block to a new location, and configure the block (using the cog icon).
» Guide to Moodle