Not very complicated, you need the Relics of Hyrule or the Hylian Shield mod, this replaces the Hylian Shield and Dark Shield models and textures with ones more like the version of the Hylian Shield from Breath of the Wild/Skyward Sword.

Download Relics of Hyrule here: http://www.nexusmods.com/skyrim/mods/40615
Or replace the standalone mod: http://www.nexusmods.com/skyrim/mods/34718
Just make sure this mod overwrites either mod and you should be good to go.