How to Add a Folder on Outlook
Go to https://www.outlook.com in a web browser. You’ll need to use a computer (instead of a phone or tablet) to use this method as these features are not available in the mobile web version.
- If you’re not already signed in to your Outlook.com account, enter your account information to log in.
Hover your mouse cursor over the left panel. A plus (+) symbol will appear next to the word “Folders” at the top of the panel.
Click + . This opens a blank box at the bottom of the folders list in the left panel.
Type a name for your new folder. This should be something that describes the purpose of the folder (e.g. Receipts, Medical).
Press ↵ Enter or ⏎ Return . This saves your new folder. 
- You can drag messages from the Inbox to the new folder.
- To create a subfolder beneath your new folder, right-click the new folder and select Create New Subfolder .
Method Two of Two:
Using Outlook 2016 and Outlook 2013 Edit
Right-click your email address in the left panel. A floating menu will appear. 
- If you don’t have a right mouse button, hold Ctrl as you click.
Select New Folder .
Type a name for your folder. It should go into the “Name” box.
Select a content type from the “Folder contains” dropdown menu. If your folder is for email, choose “Mail and Post items.” Otherwise, choose the category that best matches the purpose of your folder.
Select a location for your folder. Use the default location (Inbox) if you’re creating a folder for email messages. You can select another folder location (such as Notes or Calendar) if those options best match your goal.
Click OK . Your new folder now appears under beneath Inbox (or the folder location you selected) in the left panel.
- To move a mail message into your new folder, click the message in your Inbox and then drag it to the new folder.
- To add a subfolder to your newly-created folder, right-click the folder name in the left panel and select New Folder .