should be able to enter the tube url on the web browser but that's a bit shoddy and unreliable. the official youtube app has been discontinued but you can find a homebrew patched one out there.

there is a plugin on the hb shop that gets the official app working again, but i've found that it makes your console hang once you try to exit the app. WiiMC-SS is also an option on the vWii but it's obviously lower quality.