You have to multiply the first two terms using FOIL (First, Outer, Inner, Last). Once you have the result (trinomial / 3 term answer), take the first part of the trinomial and multiply it by the remaining term (3a + 2), then do the same for the second and third part of the trinomial. Once you have those answers, line them up from greatest power to least power and combine like terms.
Hope this helps some and doesn't make it more confusing for you.