Hi there,
thats how they display by default.
In Simple CSS you have this code:
/*Woocommerce Checkout Layout*/
.woocommerce-checkout .col2-set {
width: 50% !important;
float: none !important;
}
.woocommerce-checkout .col1-set {
width: 50% !important;
float: none !important;
}
and this code:
#customer_details+#wc_checkout_add_ons,
#order_review,
#order_review_heading {
width: 100%;
float: right;
margin-right: 0;
}
You need to remove them all to resolve the issue.