Hot wire can be found in hardware stores and feed stores. It comes in different gauges or thickness. I get the cheapest, about a sixteenth inch diameter. They all carry the 10,000 volt charge. The wire I use is more vulnerable to breakage is all.
The charge is produce by a fence charger. There are ones that cost under $100 that you must have a place handy to plug it into a power source. The kind I have is a solar charger that costs twice as much but they usually don't require being shielded from the rain like the plug in chargers. And a solar charger can be installed anywhere you need it regardless of a power source.
The charger must be grounded to a copper post sunk several feet into the soil. You attach the grounding wire of the charger to the grounding post and the power wire goes to your hot wire fencing. In my photo, you can see the overhead wire that I have hung onto the trees to clear my head going under it, and it literally ties into the wire you've installed around your coop and run.
The only thing to understand are the wire has to be insulated from anything that is touching the ground or it won't work because all the voltage is diverted into the soil. You can see the plastic insulators I have screwed into the coop holding the wire away from the building. If you have a wire fence, there are other types of insulators to fit it. Id a hot wire touch metal and you touch the metal, be prepared for it to hurt. A lot. But it's won't kill you because it's a pulse current not like in your house.
The store that sells the supplies will have someone to explain what you need. It seems mystifying at first, but really is very elementary.