Step One - go to Newgate Prison Step Two - go to Transporters (if you haven't activated them all, you'll have to run around and do so) Step Three - Hit each transporter end and look around for scrap iron, look in corners, behind boxes and water towers, etc. Step Four - Change realms - you may need to do this A LOT! Step Five - repeat until you have enough, it'll get easier the more you get used to where the little piles hide
One aspect of crafting that many find frustrating is the gathering of reagents, thus as you level you will find strategies to find, buy, and craft reagents. Scrap Iron is abundant if you know where and how to look. I am working on GH Watchtower Hall and have already found and used over 100 pieces of scrap iron, with more to go. Learning your way around MB and where scrap iron spawns will be useful, once learned you should be able to find your 32 pieces in less than an hour. Good Luck.