Woo! Thanks alot for the help guys, I got it working using the tutorial on the official site. I was having a few problems before, but the 50 page .pdf certainly helps! And I must say now I'm totally amazed by it.
It had it's own SIDs/STARs for KDEN & KLAX so I guess that helped a bit aswell.
However, I have download all of the latest SIDs/STARs and they always give me an error when I try to import them into the FMC. For example, I import KBOS and it will say something along the lines of "Error at FIX, line 28" - and this has happened with each almost every airport I have tried from the selection I downloaded, but using the KDEN & KLAX from the tutorial works. Because they causes an error I can also not choose SIDs/STARs on the route!

On another note, what is the best way to plan the route? As on the FS Flight Planner it doesn't advise what routes to use (ROCKI/CIVET etc.) - can it only be done manually by following the flight planner map or using something lke FSBuild?
Thanks!! ;)