Hi there, I'm not sure if you have the correct version of FH2, so I start by giving you this
link, which has all necessary information.
If you already have BF2 up to date (meaning patches 1.41 and 1.5 installed - in that order), then just go and dowload the
FH2Launcher and follow the instructions. If you can't log in with your old account, just select <none> and create a new one.
Good luck on the install, if you run into any trouble, don't hesitate and post here!
Btw, this is more a /Help topic, since it doesn't deal with singleplayer, I'll ask a mod to move it.