After the slats are in the open position, pull or raise the slats all the way up to the top of the window.
Once you do so, then remove the top valance piece. This is the decorative piece that covers the headrail.
If you have a wand (some blinds have 2 strings instead)that opens and closes your blinds, please remove it at this time as well.
Please leave the wand at home, but you can bring the valance in to be cleaned for just a dollar each.