There are different types of buttons:
Hotspots (empty buttons)
Text + icon buttons
All of those can be selected in the Elements tool bar. The settings of the button can be changed individually in the Element inspector.
There are many pre-installed icons. However, there is always the options to upload an SVG-file in case an icon is missing.
Buttons (SVG-files) can easily be imported with the button in the top navigation bar: