Unlocking chapters of Neverwinter Nights 1 - Original Campaign
You have to find the file nwnplayer.ini. It's in NWN's install directory (by default somewhere in Program Files or Program Files (x86) if you use a 64bit Windows, look for an "Atari" folder). If you cant find it, use Windows file search (press Windows-Key+"F") or right-click the link that starts NWN and check the preferences for details on the file path.

Open the file and find the line that starts ''CODEWORD='' (it should be in the ''[Game Options]'' section).
Change it to: CODEWORD=hacktastic

When you start a new game all chapters should be unlocked.

EDIT:
I've just seen, that you want to skip the chapters of NWN2. My answer applies to NWN1. I mixed it up, because you asked for the CODEWORD entry, which refers to NWN1.
As for NWN2, there's no way of skipping Acts that I know of. What you can do, is using the DebugMode and Script commands, to load modules, add characters to your party, fill the inventory and boost your character to your preferred level, but this is complicated and very likely to cause inconsistencies in the savegame :-/
I wouldn't suggest doing that, but if you're prepared for try-and-error it could be a solution.