I may be 100% wrong here so don't take it solely from me.

I have never even tried locating the stock fuel rails on my wrx but in my old nissan and almost every other car I've seen with a fuel rail system, the install was very self explanitory.

There are normally two bolts on each side mounting the rail with the injectors simply sandwiched by rubber gromits between the rail and the engine. Just remove the bolts, pull gently to seperate the rail from the injectors(leaving them where they are). Lift the rail a little so when you remove the fuel inlet gas does not pour all over the place. I used the foam yellow earplugs to seal the fuel line while I was working on the engine. (Works great for small coolant and oil lines) Do everything backwards with your new ones and your done.

Now keep in mind this was on a nissan 240sx with an in line four. The fuel rail was right on top of the engine and very easy to get to. This same setup was typical on almost every honda or toyo ive ever worked on. But, maybe Subaru does it different.

If my car wasn't in the shop I'd just go look and tell you for sure.
It should be a piece of cake. The flat four setup should be your only obsticle.