You can use the horizontal and vertical rulers in PowerPoint as visual cues to help you place text and slide objects. When you don’t need them anymore, you can hide the rulers.
Show or hide the rulers
To show the rulers, on the View tab, select the Ruler box. To hide rulers, clear the Ruler box.
If you select the Ruler box and still don's see the vertical ruler, you might need to turn the ruler on. On the PowerPoint menu, click Preferences > View (under Authoring and Proofing Tools). Then, in the View box, select the Show vertical ruler box.