Here is how you add two buttons and space them relative to each other.

Screen Shot 2016-03-07 at 11.53.26 AM.png

Create a new app, add a button to the middle, and then click the icon at the bottom to center button vertically and horizontally.

Screen Shot 2016-03-07 at 11.55.59 AM.png

Screen Shot 2016-03-07 at 12.00.48 PM.png

Button1 should now be centered. Add another button underneath Button1.

Screen Shot 2016-03-07 at 12.03.25 PM.png

And make it hang below Button1 by doing the following.

Screen Shot 2016-03-07 at 12.03.51 PM.png

 

Screen Shot 2016-03-07 at 12.04.01 PM.png

Screen Shot 2016-03-07 at 12.04.14 PM.png

Screen Shot 2016-03-07 at 12.05.42 PM.png

 

Screen Shot 2016-03-07 at 12.05.57 PM.png

 

You should now be done!