Press the MODE button and turn the dial to A. Aperture should stay the same so that the depth of field does not change in between exposures. Only the shutter speed should change.
Press the MENU button, and in the Shooting Menu, set Image Quality to JPEG Normal, set Image Size to Medium, and set JPEG Compression to Size priority.
Rotate the Shooting Mode dial on the top and set it to Ch (Continuous high speed). This way, you'll be able to take all bracketed exposures with a single press of the cable release or shutter button.
Press the MENU button, and in the Custom Settings menu, set Auto bracketing set to AE only. Then press the BKT button on top and turn the dial on the back to set 7 shots. Turn the dial on the front to set 1.0 exposure increment.
Press the MENU button, and in the Custom Settings menu Shooting/Display, set File Number Sequence to On. This prevents images from having the same file number.