If you are looking for hop flavor (not bitterness) move most of your boiling hop schedule to after you turn off the flame, and as suggested by others here, it helps if those additions are added after you get down to 180 degrees, so that the essential oils are not volatilized. You'll want a good 3-4 oz or more in this addition for a 5 gallon batch, and you'll want them to soak (or better yet, whirlpool or agitate) for at least 20 minutes.
For aroma, you will need to dry hop. The amount of aroma you desire will dictate the amount of hops to add into the dry hop. For a big hop aroma, you will want more than 3 oz in the dry hop. I typically use 4-5 oz/5 gal. As far as dry hopping time and temperature, that's an entirely different discussion, but the conventional wisdom is mid-upper 60's for 5-7 days. The most important factor with dry hopping is to make sure you eliminate all oxygen from the equation. Lots of CO2 and careful transfers are your best friend here.