Turn off the water supply to the tub. You will have two pipes coming up from the floor, one for hot water and one for cold. Each pipe will have a shut-off valve. Move the valve to the off position.
Loosen the pipe connectors between the pipes and the fixture with a pipe wrench. Use the wrench and work the connectors counterclockwise. You may have to use a little extra force to get them started. Place a bucket underneath the pipes because they might leak when you loosen them.
Remove the old fixture from the clawfoot tub by loosening the caulk between the tub and the fixture. Insert a pry bar between the two and gently pry them apart. Thread the ends of the fixture out through the holes in the tub to remove them.
Install the new fixture onto the tub. The diverter will have two pipes to connect to the water supply. Thread these through the holes in the tub. Connect them to the water pipes with your pipe wrench.
Caulk around the new fixture with silicone caulk. Lay down a quarter-inch bead around the fixture ends and press it firmly into the tub.
Attach the diverter support to the wall or a cabinet. The diverter section of the fixture will be around 6 feet high. It will have a small clamp mid-way up that needs to be attached to something solid to provide it support. Screw this into the wall or cabinet with a cordless screwdriver.
Hang the new shower surround curtain fixture above the tub. The curtain rods come in D or U shapes. They will have connectors that can either be attached to the ceiling above, or the wall over the tub. Center the rod over the rub and screw the hardware into the wall or ceiling with a cordless screwdriver. Hang the shower curtain on the rod.