Single Product Page on Upfront Theme - Huge Empty Space

There's a HUGE empty portion at the bottom. Where do I add the code (as mentioned in this thread: https://premium.wpmudev.org/forums/topic/marketpress-single-product-page-on-upfront-theme#post-1046692).

.mp-multiple-products.mp_product_tab_content.mp_product_tab_content-related-products {bottom: 0;}
.mp-multiple-products.mp_product_tab_content.mp_product_tab_content-related-products.mp_product_tab_content-current{bottom:initial;}