Hello
Tman10117! Welcome to the forum! We would love to help you out! Strapping of armor is an age-old question and everybody has their own way of doing it. Unfortunately, there's not really a standard way (at least not one that I know of). I am also working on an ODST and have been struggling with strapping almost as long as I have spent actually making the armor.
To figure out what piece goes where, you can do a simple Google search for ODST armor or check out the rookie cosplay guide put out by 343i. I'm sure there's a link to it somewhere on the forum... Generally, there's a helmet (should be fairly obvious), two shoulder pieces (big squares connected by a smaller square), two forearms (generally cylindrical in shape) one chest piece (doesn't look like it would fit anywhere else) with attached or maybe not attached an pieces, two thighs (probs the only pieces with holes big enough for thighs), two shins (weirdly complicated tubes with a flat front), and two boot covers (small arched pieces).
personally, I have been using snaps to secure the shoulders, friction to secure the forearms, and I'm working on the leg pieces as we speak. The chest plate for me is hard but I'm going to use the weird backpack straps that may or may not have been included in your purchase to hold the chest in place. A lot of people use Velcro, or nylon straps that connect to your belt or w/e. I would suggest looking at various builds to get ideas. Also someone else may post after me with a great idea!
That's a great thing about this forum is there are all kinds of people with all kinds of knowledge and experience.
Here is my build
ODST Build 1: The Journey Begins
There are some good reference images on page 4 (maybe 5?) And eventually I will post stuff about my leg strapping when I finalize it.
Welcome to the party!