Great,
as soon it comes in, install it and let it run.
It might very likely overflow after a few hours or even minutes.
Route a hose to a bucket and catch out the wet foam that is being produced.
you might end up with 3-6 Gallons of very wet foam before the skimmer starts getting foaming normal.
This is due to the excessive waste in the water.
I will post the magic receipe you need to mix very soon, which you need Svedska Vodka (buy at Specs or Liquor store), Heintz white Vinegar and regular white sugar and a bottle of 0.5L that you can use to contain the so called VSV mix.
In addition you need to purchase a 12 or 16 ampule containment of "Biodigest". Amazo I found the cheapest ones. Keep in mind only biodigest, nothing else, no need for a combo package that also contains bacteria food, that is already present in your tank.
A few days after the skimmer ran nicely we will start the VSV dosing and increase of bacteria population and bring the tank slowly back to life.
I won't bring your tank to an ULNS status, but will significantly lowering your nutrient level similar to the Biopellet method, but more controlled.
So start looking into those ingredients.