To install, simply download the Zip file and extract the contents to "My DocumentsBioWareDragon Agepackagescoreoverride". This may be a different path if you're using Windows Vista or 7.

If you don't want the difficulty level changes remove difficulty.GDA.

If you don't want the Poultice/Pickpocketing changes remove ABI_Base.GD.

If you don't want any monster damage scaling remove all the .uti files that start with gen_im_cweapon_.

Any other .uti files are item changes.

You will need to start a game from scratch for all of the changes to take effect. You do not absolutely have to restart, but any items that already dropped will not be the modified versions, as the game's structure does not work that way. There is no way for us to get around that. You can play it and the changes will take effect, but only in areas you have not explored yet.