how do you use the half hole?!?!

Assuming you mean the thumb - just open your thumb a little bit - one instructor says, "Just crack it open a little," and this allows you to play up an octave. You can experiment with how much to open your thumb. Not much, usually. Some people like to stick their thumbnail into the hole but I find this hard to do.

If you're talking about playing low E flat or D flat, most soprano recorders have two holes for the D and C fingers. Opening up the fingers to expose one of the holes gives you the E flat and D flat. I guess this might be called a half hole but I never thought of it in that way.

you would see more half holing with a tin whistle. It is exactly that, cover half the hole. On a recorder the only hole that needs to be half covered is the thumb.