SO i just got into warhammer recently and i built an army but i am habing problems understanding formations and how they apply with my army.

I got the infiltration cadre and purchased a broadside, devilfish, xv8 crissis team, and a fire warrior squad. As I understand it i have the infiltration cadre formation rules applied to the pieces from the box set and not the others i added to my army. I am looking to purchase the retaliation cadre box set and I read some where that they have their own formation rules. I was wondering if I was able to use both sets of formation rules at the same time or not and if I am not understanding a core concept here at all.

Thank you Very much.