To add the button press + and choose Button under Basic Componenets:
Use Props menu on the right to edit your button.
Here you can:
add text to your button
add link or email ( Note: To add an email type:
mailto:someone@yoursite.com
)change buttons' variant, color and and size
add icons or animations
Use Design menu on the rigth to add padding or hide for screen sizes.
To edit the color of your button press Paint Bucket and choose one of the Website colors, Gradient colors or your color.