Go to the Dashboard, then click "Pages and Themes" from the left sidebar, then click the "Page Types" tab up top, then click the "Defaults" button next to the page type you want to set defaults for. Now any blocks you add here will automatically be placed on new pages of that page type (you'll have to repeat for every page type in your theme). If you want to add these blocks to pages that already exist, click on the block and choose "Setup on Child Pages" (but note that if you've already added blocks to pages that already exist, you don't want to also do the "Setup on Child Pages" because it will add a second one).

Hope that helps.