This is a DLL file which adds ASI plugin loading functionality to any game, which uses any of the following libraries:
dinput8.dll (x86 and x64)
dsound.dll (x86 and x64)
version.dll (x86 and x64)
wininet.dll (x86 and x64)
With the last two, it is possible to load the original dll by renaming it to 'vorbisHooked.dll' or 'binkw32Hooked.dll'. Usually it is not required and you can simply replace the dll. Always make a backup before replacing any files.
In order to install it, you just need to place DLL into game directory. Usually it works as dinput8.dll, but if it's not, there is a possibility to rename it(see the list of supported names above).
Put ASI files in game root directory, 'scripts' or 'plugins' folder. If configuration is necessary, global.ini file can be placed to 'scripts' or 'plugins' folder. It can be used alongside the chosen dll and if so, it is also possible to use dll name for ini file, e.g. version.dll/version.ini. See example of global.ini here.
ADDITIONAL WINDOWED MODE FEATURE
ASI loader have built-in wndmode.dll, which can be loaded, if you create empty wndmode.ini in the folder with asi loader's dll. It will be automatically filled with example configuration at the first run of the game. Settings are not universal and should be changed in every specific case, but usually it works as is.