Hi there and welcome to FTB!
I'm somewhat new myself, but I'll share what I can as I know how daunting it is to step into FTB for the first time.
Your first step is picking a mod pack! If you have any youtubers you follow who play FTB, you will probably want to choose whichever mod pack they use. If you don't follow any youtubers, here's a good comparison of the mod packs (granted, I know it's gobblety-gook if you don't know what the mods are... so this is some homework, honestly:
http://feed-the-beast.wikia.com/wiki/Feed_The_Beast_Modpacks). I personally use FTB Ultimate, though I could probably just as easily switch over to the MindCrack pack. Each pack basically offers a different flavour of the FTB experience from magical RPGing all the way to high-tech nerdery.
Once you've picked a pack, you may want to do a Google (or other) search for "[mod pack] getting started". Searching for "FTB getting started" brought me to this wiki post:
http://feed-the-beast.wikia.com/wiki/Getting_Started. It seems like an alright entry, but it fails to mention the GregTech mod which is included in some packs (like Ultimate and MindCrack) which essentially makes the game harder (harder recipes, etc) in order to slow you down and ensure you don't get to "end game" status too quickly.
Unfortunately, a lot of the information I find online doesn't really account for GregTech, so when looking up recipes your best bet is to use NEI (Not Enough Items) directly in-game. When you open your inventory you'll see a large grid of all the blocks in your mod pack displayed on the right-side of your GUI. You can right click any of these or press R to bring up the various recipes on how to create this item. You may see arrows at the top which will switch between the various means of crafting such as shapeless crafting, shaped crafting, smelting, etc and another set of arrows at the bottom which switches through the various recipes within that means of crafting. It may take some getting used to, but this is invaluable.
I think I'll cut it off there for now! If you have any questions, feel free to ask in the forums and I'm sure you'll get loads of help/opinions!