You can screenshot by pausing your game and then going to miiverse from the pause menu, then make a post and select screenshot. At least, thats what I remember..

I dont think you can screenshot any other way, i'll check when im home with my wii u

you need the screenshot plugin from the HB app store and then press left on d-pad and the tv button then go to miiverse and select the screen shot from either you're tv or gamepad

the photos you can both get the screenshot manager plugin which crashes often, the wiiu shell plugin to get to the screenshot folder view them delete copy paste all that or you could use your pc and access them that way. I use wiiu shell or my pc

sry for my rambling...