If you downloaded it as a Zip file then open it and find the uninstall option, it should be in there
Otherwise you can delete stuff of a pc in a number of ways,
1) you could type the file name (such as "Feralhearts" into the "Search Computer" box in the start menu. if its on your computer this should find it.
2) Have a look if its listed in you "add and Remove Programmes" if it is just click un-install
3) If you installed it in firefox have a look in your download history file, it should be there.
Otherwise remove you could completely un-install the game, than re-install it
Hope one of these helps