Clicking the Page Zones button (ti ti-columns) will enable the zone fly-out menu for each zone defined on the page. From this menu you can bring up the zone dialog below. From the zone dialog you can add or delete blocks in a zone. The tabs at the top of the page determine if the blocks will be added to the current page, the layout or the site. Adding the block to the layout will enable it to be shown on all pages that use that layout. Adding the block to the site will place the block on every page in the site.