You can show rulers to help you position and align objects, and hide the rulers when you don’t need them.
Click 
in the toolbar, then choose Show Rulers or Hide Rulers.
To show size and position coordinates when moving objects, choose Keynote > Preferences (from the Keynote menu at the top of your screen), then click Rulers at the top of the preferences window. Select the “Show size and position coordinates when moving objects” checkbox.
When you set a unit preference for rulers, it applies to all presentations. You can change the preference at any time, even if you have a presentation open.
If you don’t see the ruler, click in the toolbar, then choose Show Ruler.
Choose Keynote > Preferences (from the Keynote menu at the top of your screen), then click Rulers at the top of the preferences window.
Click the Ruler Units pop-up menu, then choose an increment (Points, Centimeters, or Inches).
To show the ruler marks as a percentage of the slide, select the “Display the ruler units as percentage” checkbox.
You can place zero at the center of the ruler, which means ruler units increase to the left and right.
Choose Keynote > Preferences (from the Keynote menu at the top of your screen), then click Rulers at the top of the preferences window.
Select the “Place origin at center of ruler” checkbox.