And he really means STUFF! The valise is a compression sack (well, it's supposed to be a compression sack). Anyway, Gunner is completely correct, those bags are meant to be crammed in there. If the valise is (fairly) new, it may be one of the water-proof ones...don't trust it. Line your valise with the bivvy bag (as long as there are no holes in it) and stuff your bags in to that. stuff stuff stuff it all down, squeeze the air out, fold the funny shaped lip of the bivy bag over itself, groundsheet, wash basin.
If there is enough room for a pillow (no, I am not kidding. I take a pillow everywhere. Not a gargantuan one or anything, just right for my little noggin) in with your sleeping bags, then you've done it right.