The 'Button' element can be used in any part of the site.
You can find the element below the tab 'Content elements' when creating a new element. (1.5.1)
In the 'General' tab you can see the content element type 'Button' selected (1). (1.5.2)
The element uses the button text field (2), link address (3).
In additional setting you can choose 'Button Size' (4): in a drop down menu there are 3 kinds of size available Large, Small, Extra small;
You can also set the 'Button Style' (5) - below you can see several examples of style;
And with a help of 'Block level button' (6) field you can make the button for a full width view (like on the button with Style 'Warning' below)