Once you have created your artwork you need to extend any backgrounds, images and graphics close the edge of the page manually, then use Illustrator to specify the extended amount of bleed.
Once you have created your artwork you can then use Illustrator to specify the amount of bleed you require, then extend any backgrounds, images and graphics close to the edge of page to fill the bleed. Adding bleed makes Illustrator print more of the artwork that is located beyond the trim marks. The trim marks dictated from the artboard size still define the size of the page.
Standard bleed size is 0.125” on each edge of the page but if printing large format prints then 0.5” on each side of the page is required.