Hi i'm new here and i love his forum, but can someone help me make HD textures in games, please it would mean so much to me

I know how to make texture resolution from: eg: 512x512 to 1024x1024 and like that.
And i know how to create normal map.
But how can i make textures HD to add more details like in Oblivion's Qarl's Texture Pack III
http://pnmedia.gamespy.com/planetelderscrolls.gamespy.com/fms/images/oblivionmods/2363/1170363661_fullres.jpg

And in Skyrim 2K HD Skyrim Texture Pack
http://static.skyrim.nexusmods.com/mods/images/607-3-1322170188.jpg

Does anyone know how to add details like that to vanilla textures or some website tutorial for it ?
Thanks.

I use Photoshop BTW