Customize my account page

Try this custom css:

@media only screen and (min-width:768px) {
.woocommerce-account .woocommerce h2:nth-child(1),
.woocommerce-account .woocommerce form:nth-child(2) {
  float:left;
  width:47%;
  margin-right:5%
}
.woocommerce-account .woocommerce h2:nth-child(3),
.woocommerce-account .woocommerce form:nth-child(4) {
  float:right;
  width:47%
}
.woocommerce-account .woocommerce h2:nth-child(3) {
  margin-top:-59px
}
}

If your theme does not have a setting where you can enter custom css, you can use a plugin like this one:
https://wordpress.org/plugins/simple-custom-css/