Download CudaMiner.
In the same folder where cudaminer is, create a new file, name it: Launch.bat(Name doesnt matter, make sure the extension is .bat)
Rightclick the file and click edit. Paste this into it:

cudaminer -o http://miningpool.nl:8332 -O YOURUSENAME.MINERNAME(Default:1):PASSWORD(default: x) -l 28x8 -C 2

Depending on your GPU you can play around with 28x8 see: https://github.com/litecoin-project/litecoin/wiki/Mining-hardware-comparison#wiki-Nvidia_GPUs

Here is a screenshot of how it should be:
http://i.imgur.com/ZMBxliI.png
Ofcourse my username should be replaced with yours

Cheers,

-C