Regarding forum:
- there exist many open-source forum software packages, you have to pick one and install it. Duelboard uses this one
http://www.simplemachines.org/ (but I'm not saying it's good or bad, there maybe exist better or worse, I picked it almost randomly).
The installation should be simple, you just download the installation package, then you have to upload it to your hosting computer and unpack it. To unpack the files you probably need shell / console access to that computer. If you don't have it, you probably have to unpack it on your computer, and upload all the files (there are many of them).
Once it's all uploaded, you'll have to open some html file (maybe something like install.html, you'll have to read the documentation), and it will show some installation form. You'll have to fill in stuff like database password etc, and it should install the forum then.
I remember that I had some issues with file attributes and permissions, so it's possible that you'll need console access anyway (they may call it SSH access). Well you'll probably also need some Unix skills (if it runs unix operating system)