The forge, anvil and vise should be within one step of the center of your circle, otherwise you will have more mileage on you than a '57 Chevy. The power hammer should be two steps away and everything arranged so there is a clear path in and out.
Set the forge, anvil, and vise out in the yard and forge a couple of weekends. Move things about till your comfortable then take notes of the locations. Plan now on how to get the smoke out of the building and where to locate the chimney. That will locate the forge, which will locate the anvil, vise and well you get the idea.
If you have ever seen a working blacksmith shop, you will find a lot of dust and fine powered dirt, swarf, etc. Air compressors do not like dust, move it outside or to a closed closet with outside air intakes. And you may want to put the air compressor on a dedicated circuit.