There are two basic ways to use it.
One way, you just change the genes and see how the picture of the chicken changes. So for your cross, for the first dropdown box, I would select E/E^Wh because the chicks will inherit E (Extended Black) from the Chocolate Orpington father, and E^Wh (Wheaten) from the Production Red hen. Keep going down the list, setting the genes you know about, and see what the result is when you reach the end. For your cross, probably the only other gene that matters is chocolate: Choc+/choc for the sons because they inherit chocolate from the father and not from the mother, choc/- for the daughters because they inherit chocolate from the father and nothing from the mother (chocolate is on the Z sex chromosome, but the mother is giving a W chromosome to make them female.)
The other way to use the calculator is to change the genes until the rooster matches your rooster, and the hen matches your hen, then click the button that says "calculate crossing." Then calculator will tell what chicks to expect from those parents, and show them to you (if you don't see them, scroll down or up and look around. There are several slightly different versions of the calculator, and I think they sometimes display the offspring in different places.)
https://kippenjungle.nl/chickencalculator.html
This is the version I was playing with just now.
For all the versions of the calculator, if you need to put the genes back to their default settings, just choose the ones marked with +
Those genes are the original wild-type form, found in the wild Red Junglefowl ancestors of chickens, and all the other forms are mutations of them.
Sons should be black with leakage, but the leakage might be red or white/silver.
Daughters should be chocolate, also with leakage (again, leakage could be red or it could be white/silver.)
Because the sons will be black and the daughters chocolate, they are one kind of sexlink (color-sexable, assuming you can tell the difference between chocolate and black by looking at them.)
