I'm asking what to do with the small ISO once it's been put onto the SD card. I'm guessing I launch it via Nintendont, from the answers already given.
I see

:slaps forehead:
In my defence, though - from what I've seen so far, Nintendont runs when you boot up a game, not the other way around. I haven't installed Nintendont before because AFAIK there
isn't a way to install it directly onto Wii U, only via vWii which (as I've mentioned) I'd rather not do. I'm coming around to the idea that I should probably do it, though, and probably will.
You shouldn't (necessarily); the question was really meant for anyone who has had experience with that particular forwarder, or who might know how forwarders work with Tiramisu in general. From what I understand, it doesn't play nice with forwarders.
//EDIT: Happy to move all further discussion regarding this to the
Nintendont thread to keep it all in one place!