src/Checkout/Checkout.php
public function setShippingAddress(Address $address)
    {
        $this->order->ShippingAddressID = $address->ID;
        if ($member = Security::getCurrentUser()) {
            $this->order->MemberID = $member->ID;
        }
        $this->order->write();
        $this->order->extend('onSetShippingAddress', $address);

        ShopUserInfo::singleton()->setAddress($address);
    }
public function setShippingAddress(Address $address)
    {
        $this->order->ShippingAddressID = $address->ID;
        if ($member = Security::getCurrentUser()) {
            $this->order->MemberID = $member->ID;
        }
        $this->order->write();
        $this->order->extend('onSetShippingAddress', $address);

        ShopUserInfo::singleton()->setAddress($address);
    }
save / set up addresses