Add this code to the text area of your slider
<a class="et_pb_more_button et_pb_button slider_button_style" href="#">BUTTON 1</a> <a class="et_pb_more_button et_pb_button slider_button_style" href="#">BUTTON 2</a>
Add the following css to style the buttons
.slider_button_style{color:#fff;background-color:#ccc;border-color:#000;}