It's the app that has a blue icon with an image of a cover with an "O" over an envelope. If you don't have the Outlook app on your desktop, click the Windows Start icon, and type Outlook.  This will display the Outlook app in the Start menu. It's in the menu bar at the top of the screen. On Mac, skip this step. It's the icon that has an image that resembles blue text in a sidebar.  This will display a drop-down menu. On Mac, click the envelope icon in the bottom-left corner instead. This will display the Folder Pane in a sidebar to the left. On Mac, skip this step. Click the small triangle to the left of your email account to expand all the email folders and categories associated with that account. Click the Archive folder in the column on the left to display all the archived emails in the pane on the right. You can search archived emails using the search bar at the top of the email list pane.  Use the drop-down menu next to the search bar to select "Archive Folder".

Summary:
Open Outlook. Click View. Click the Folder Pane icon. Click Normal. Click  next to your email account. Click Archive.