Welcome and well come to the Archive, Dragonhelm. May your stay with us be long and profit you greatly -- and I think it will.
Peter Fuller is darn good and highly respected, but I think you'll get more initial bang for your armor-buildin' buck, and at about the same price too, getting yourself a copy of Brian Price's
Techniques Of Medieval Armour Reproduction: the Fourteenth Century. (ISBN 1-58160-098-4) (As Thomas said.) It's not a biology text and cannot be mistaken for the Kama Sutra.

That reads more like stereo instructions than pornography anyway. Try Amazon, AbeBooks, Half Price Books, and eBay. It's not just about making helmets, but about everything, head to foot, with chapters on method, design, equipping a metalworking shop, even mail and designs for fourteenth-century arming coats, which were an essential component of these early-mid suits of armor.
Get the Fuller later.
Meantime, have a look at the how-to articles on this site and take notes for questions. Search the site on terms and many of your questions will surely be answered.
One thing we should ask is how much of a shop do you presently have access to? One kid recently answered that question with, "A Dremel." Well, only direction he can go is up, so it's not all bad. Armourers tend to collect hammers. Starting off with one big hammer and one small one is good. The small one should be a ball pein, 16 to 24 ounces. The big one is for dishing and serious metal moving.
Other things to get: every shape and size of file, at least the smallish and middle sizes. Big ones, if and when. Some means of cutting sheet metal; cheapest one is a good saber saw and a fistful of blades and a few wood blades too for making wooden stuff with -- handles, shields, and a few clever gizmos. Some means of making holes; an electric drill or a sheet-metal punch, which is more expensive but makes finished holes in seconds, not a minute per hole. Something to dish into, which could be anything from a bare patch in the ground to a tight-packed sandbag to a hefty wooden stump. Clamps: assorted C clamps and every size and type of Vise-Grip locking pliers. You'll have use for every one of 'em. You can buy or make stakes to form things over.
You don't really need an anvil. But if there's one already around... Your profile says your occupation is blacksmith, so there should be very darn few tools you CAN'T make. You're better fixed for toolmaking and hotwork than 95% of the posters here.
Armourers collect even more assorted stakes to stick in a heavy stump or whatever (many ingenious whatevers, too) than they do hammers. An anvil's hardie hole is a pretty good holder for armoring stakes.
Eventually, the serious armourer finds himself learning to weld. Community colleges have courses on the valuable skill of how to weld without blowing your shop up, getting thoroughly electrocuted, or setting things on fire that aren't supposed to be on fire. Dealing with hot stuff is like that...
"I'm wanting to start to make armor and . . ." is quite the FAQ -- and it's also like saying "How do I make an airplane?" without further specifying whether you want a Piper Cub, a Sopwith Camel, or an SR-71. Armor went through many periods and lengthy evolution, and even nowadays, one must look at what one is using it for: LARP gaming? Society for Creative Anachronism? Living History reenactments? All these have their particular demands and their specific threat environments, and we get EVERYBODY here, so we always have to sort out just which we're talking to in order to give good advice and suggestions. Don't be afraid to pester us with questions; we're here to be bothered and we like to talk, or we wouldn't post here at all. Personally, I have to ask the dumb questions before I know enough to try the smart ones, but with reading, particularly on this site, YMMV.