When you're using cooked spinach in a dish like lasagne or quiche, or dip, you usually need to squeeze out the extra water, so it doesn't make the dish all soggy. One common method is to roll it up in a dishtowel and wring. That works, as long as you don't mind staining your dishtowel all green. But, there's a better way.
You may have a gadget in your cabinets that will work just as well to dry the spinach, but without a lot of work or mess: a potato ricer. Basically, it works like a giant garlic press. Just put a handful of the spinach into the hopper, and squeeze it dry over the sink or a bowl.
Now your spinach is nice and dry, ready to layer into lasagna or fold into a dip.