If you are using a USB flash drive as the media for your wii roms, you will need a program called 'Wii backup manager', you can put those games onto your flash drive by selecting open file under the files tab and selecting the converted iso. No, nkit.iso's will not run on the wii, however you can convert them to ISO's with the nkit processing app The best guide for homebrewing your wii is here: You have to make sure to follow instructions completely and do research before installing applications.
Hey! Homebrewing your wii is as safe as you are careful.