Hello,

You will need to add this CSS code in to Theme Settings > Custom CSS:

.woocommerce-my-account-wrapper{
    display: -webkit-box;
    display: -ms-flexbox;
    display: flex;
    -webkit-box-orient: horizontal;
    -webkit-box-direction: normal;
        -ms-flex-direction: row;
            flex-direction: row;
    -ms-flex-wrap: nowrap;
        flex-wrap: nowrap;
}

 .basel-my-account-sidebar, .woocommerce-MyAccount-content {
    float: none;
    display: -webkit-box;
    display: -ms-flexbox;
    display: flex;
    -webkit-box-orient: vertical;
    -webkit-box-direction: reverse;
        -ms-flex-direction: column-reverse;
            flex-direction: column-reverse;
}
.woocommerce-MyAccount-title {
    -webkit-box-ordinal-group: 2;
        -ms-flex-order: 1;
            order: 1;
}
.woocommerce-MyAccount-content {
    float: none;
    display: -webkit-box;
    display: -ms-flexbox;
    display: flex;
    -webkit-box-orient: vertical;
    -webkit-box-direction: reverse;
    -ms-flex-direction: column-reverse;
    flex-direction: column;
}

If you have any questions feel free to contact us.
Best Regards