How do you watch it on a Wii U? 

You can't stream it on Wii U, but you'll be able to watch the replay in the eShop

EDIT: you may be able to watch it live on Youtube, via Wii U's internet browser.

Is the stream not available on the eShop?

The Web browser, and go to Twitch or whatever site is the best.

I watched the ign stream yesterday on the Wii U browser. No hiccups and hd.

Twitch didn't work.

Yep, like laststarfighter said. You gotta use the Wii U web browser because I doubt the eshop has a live stream. Eventually the eshop will get the videos but not live stream.

you cant do that. you are not allowed to stream anything on wii u not wii u related.

I wish the eShop had livestreams :/

What's so good about eShop trailers? I never use them, the high quality eShop trailers all stop to buffer constantly.

Meanwhile the HQ youtube videos in Miiverse stream nicely, they just don't set HQ as the default option.