This is best boosted as you need quite a bit of skill to get it legit. Just be aware that the matchmaking is straight out of hell.
There are two types of support. Offensive and defensive. As soon as a support is available you have to press
for the offensive type or
for the defensive type.
To get the Apache support you have to get a 2300 point streak. If you get killed before amassing the points needed...start over friend. If you get killed after hitting the 2300, don't worry. You'll keep the support.
Once available hit
on the D-Pad and you'll find yourself in the chopper and the Trophy popping up seconds later.