Need guide, complete newbie here.

I just herd about this software yesterday and i wanna use it. i thought it cost money because it is paid on steam but apparently there is also a lossless scaling website which has it for free, i cant tell if there is a difference between these two version? should i opt for the paid one or free one?

Also can someone give me a link to some guide to use this? i wanna increase my fps on Skyrim (steam)