When you download something it usually shows up in the computer's regular Downloads folder (if it doesn't, maybe change that in your browser settings or just check there where your files go) and could be the package file you want or just as well a zip or rar file you'll have to unpack. Then move the package files to Documents > Electronic Arts > The Sims 4 > Mods. If the Mods folder doesn't exist, just create one. The eyes could be default (meaning they'll automatically replace the normal eyes) so you won't have to select them somewhere in-game. Then there is non-default, usually found under skin details in the face section (the lashes are probably there as well). Third possibility is a facepaint version. Since you watched so many videos, I'm not sure whether this could help, but if not and if you explain your problem a little more I'd be happy to try to help you anew.