So what is a hot bed? It is different from a cold frame in that it is dug several feet into the ground, and is heated with manure. You put a layer of fresh manure on the bottom and add a layer of soil on top to plant in. The manure heats as it decomposes, making a warm environment inside the box to grow things. That is why it's called a 'hot' bed!
Pick a spot with good exposure to the sun, preferably on a south-facing slope. Mark the spot by laying the window on the ground and scratching an outline.