Making a shield will take some time, even if you are a proffesional blacksmith,the tools you are gonna need are:
3 ingots(any type) a hammer(duh) a blacksmith(duh) and a log(not firewood) and be in sandbox mode,its not availabe in shop mode.
now youre gonna need to take the log to the cutting station/table,itll bring up a menu of shields, choose your shield then look down at the thingy under the table and press left click, it should cut it , now bring it to the table of attaching. heat up the 3 ingots, put one on the anvil , hold z, select the shield section and hammer it, now it should turn into a circle thing, attach it to the center of the shield, reapet the procces from "put one on the anvil" 2 more times, but in the 2nd attempt turn it into a hand handle, 3rd turn it into the elbow handle. and attach them.
hope this helped you with your blacksmith carrer, from the blacksmith,Basool