Are you using any control panel like Cpanel? If so, it can be installed with 2-3 clicks.Otherwise, you have to manually download its tarball and install. Its a simple procedure and its instructions would be there in its INSTALL file.
phpBB is a security disaster and needs frequent urgent updates. If I was a newbie, knowing what I know, no way would I run it on my servers. I've actually removed it from Fantastico for that very reason on my servers.
SMF - aka www.simplemachines.org - is a much better option. While not as popular it has much more modular design and can be easily upgraded with only a few clicks if a security problem comes out, and modules can easily be added.
Hopefully phpBB will come out with something similar soon (ie an ability to upgrade easily from within phpBB) but at the moment they're just hopeless. Avoid them like the plague.
Eh i still use phpbb on one site but its a pain in the *** when it comes to fighting spam bots even if you turn on the captcha and email validation. Also its limited in features and if you add new features be prepared to spend hours reinstalling those features if you have to do an update.
SMF rocks. I've been using if for a couple of years now and love it. Its comes with quite a few default features missing in phpbb. Also new features are written as plugins so you dont have to "usually" worry about screwing something up after an upgrade. The forum upgrades are also done automatically.
I do get a spam bot once in a while but that sonly if I have an open registration set up. If I set up captcha and email validation I dont get any spam bots. Thats not to say this will be so once SMF get more popular.
+ NOW WE'RE MAKING RECORDS, NOW WE'RE MAKING TAPES