put div in the middle using flex code example

Example 1: flexbox align center vertically

.Aligner {
  display: flex;
  align-items: center;
  justify-content: center;
}

.Aligner-item {
  max-width: 50%;
}

.Aligner-item--top {
  align-self: flex-start;
}

.Aligner-item--bottom {
  align-self: flex-end;
}

Example 2: flex align children to side

flex-direction: column;
align-items: flex-start; //left
align-items: center; //center
align-items: flex-end; //right