I'm so so confused on how to factoring problems that have trinomials..

just as an example i have 3x^2 + 7x +2

i'm jst getting really confused and i need someone to explain it to me in SIMPLE words, my teacher is really confusing

so basically with the problem i gave above i need to factor it completely, and then pick one of the factors and match it with a column thats adjacent to it..but that's what i'll do after someone explains HOW to factor!!

please help

(just for some more examples

3x^2 - 16x + 5

7x^2 - 9x + 2