Step 1: Navigate to your desired presentation within your Deck and then click to go into that specific presentation.

Step 2: Click the "Presentation" drop-down from the top-left and then "View Presentation". This will open up your presentation in a new window and tab to showcase.

NOTE: If you would like to view this window in a full screen, you can hit "CTRL+CMD+F" if you are on a Mac computer or "F11" on a Windows computer.