Because of it’s limited use, the Notes folder is a bit more obscure. You can still access it by clicking on the Indicator next to Tasks. Simply click on the three dots next to the Contacts symbol and you will see some choices.
To make it permanently visible, follow the steps below:
Click on Navigation Options.
Click on Notes and either move it up or increase the Maximum number of visible items from 4 to 5.
If you followed the steps above, the bottom of your Outlook screen should now look something like this: