Stretch your design to the full bleed to avoid white borders on your printed product.

Here's how you stretch a design to the full bleed:

Select the image
Move the image to a corner
Drag the image to any corner of the design area. When the image reaches the safety margin, it'll automatically move to the edge of the print area.
Select the handle
Use the handle in the opposite corner. If you don't see the handle, make sure the image is selected.
Increase the size of the image
Resize the image until it covers the entire print area.