Get yourself a cheap plastic bin from Target and use the templates to cut out the armour, you will need to heat the plates up to bend them to form around your body. So, as mentioned, print out the templates and check to see if you get good coverage but not so the chest plates go past your rib cage.
I would recommend that you get a vest before you shape the plates as the vest tends to muffle the body's general shape.
If you are looking to troop in the armour then try the mandalorian mercs, as they have guidelines for how the suit should look, there are also some great tutorials stickied in this section as well, two which I think would be useful to you are the helmet sizing guide and the plate mounting guide.