How attach a new shower body valve

It sounds simple to do but when I got the new shower kit the valve part does not have flanges with screw holes to attach it. How do I set it in to stay securely?

I could post a picture if I knew how???

I just did this with a Moen valve and, like you, was looking for flanges. However the directions show the valve supported by the supply lines, copper in my case. That has worked fine. My trouble was visualizing the spacing fore-and-aft in the stud cavity. The directions were nearly useless and designed for someone replacing the faucet rather than doing it as new work from scratch.

What's your situation?

That's the exact situation for me... Directions useless. So far I put a stud in horizontally and was going to "zip tie" it in place. I just can't imagine it staying in place otherwise?? Thank you for your input!

Use some copper pipe straps on a brace screwed behind the valve to the supply lines. If your pipes go horizontally through studs, the holes will help stabilize things, but not enough.

Great! Thanks!