how do i center buttongroup reactstrap js code example

Example 1: how do you center buttons in css

<div style="text-align:center;">
    <button>button1</button>
    <button>button2</button>
</div>

Example 2: how do I add a vertical margin in css

subject {
  margin-top: /*the size of the margin */ (example: 100px)
  /* or */
  margin-bottom: /*the size of the margin */ (example: 100px)
}