From the Gear menu (Cog icon) in the top right corner of your course page, click Turn editing on.
Open the Nav Drawer (if necessary), using the Hamburger menu, top left. Scroll to the bottom of the Nav drawer and click Add a block.
A list of block types will appear. From this list select the type of block you would like to add to your course.
The new block will now appear in the right hand column of your course, usually at the bottom.
You can then edit and configure the block information by clicking on the Gear menu (cog icon) in that block; or move it to a different position by using the cross icon to drag it up or down.
If you would like to remove a block, go to the Gear menu (top-right within the block) and select the delete block option .