Office 365 (Outlook on the Web) - How to Create a New Contact
if you are in Mail, Calendar, or Tasks, select the People icon from the navigation bar on the left - OR - if you are in another application, go to the top of the page, select the App launcher 
, and then select People.
1. To create a contact, select New Contact>New Contact.
2. This will open a blank contact form. Fill in any details that you want. Select Add more to bring up additional field options.
3. When you’re done, select Create to save your changes or Discard to cancel.
For the most current information on creating a new contact via Outlook on the Web, please check out the following Microsoft help article: https://support.microsoft.com/en-us/office/create-and-edit-a-contact-fff455df-7470-4648-9696-9400e9da5eab