You can find the latest versions of sweetfx and any related news at the Guru3d forums here: http://bit.ly/1fdhjWc - this forum is also a good area to look for any technical support related to sweetfx as it can be finicky with some hardware setups. In addition you can go here http://sfx.thelazy.net/games/ for a constantly-updated database full of sweetfx presets for all kinds of games.
The installation process as I mentioned is painless and easy to reverse should you encounter problems with sweetfx or just not like it/etc. The sweetfx readme also describes this process - simply find the game's main executable file (for hawken this will be in C: program files (x86)/steam/steamapps/common/Hawken/binaries/Win32), open the sweetfx folder/zip, and copy all of the sweetfx files into that folder where hawken's executable file is. If you start your game now you won't see any visual difference as at this point sweetfx hasn't been configured to actually inject any effects, so you'll need to edit the 'sweetfx_settings' document. Customize to your heart's content. Once you're finished, save the document and launch your game to see your new effects in action!
Here are some hawken-specific presets that have been made by myself and other forum members - if you've got your own that you'd like to add, throw it up onto pastebin and into the thread!
my own "Subtle Saturation" preset:
comparison: http://imgur.com/a/3qeNw#0 - pastebin link: http://pastebin.com/c41XpW3w
Kopra's "Desaturated Demolition" preset:
comparison: http://i.imgur.com/1Ped1yz - pastebin link: http://pastebin.com/ygighWzt
Edited by Beefsweat, July 04 2014 - 10:45 PM.