The first step is to launch the "hackmii installer" from the homebrew channel, is that what you meant? Or do you literally mean you can't launch "bootmii".
Honestly please tell me specifically what the issue is. For example, you could say "I am in the homebrew channel, I press home, I select" bootmii" and X happens instead of loading bootmii." Or better yet, copy the section of the guide you are at (assuming you completed all previous steps successfully) and highlight the problematic area, and what it is you're experiencing.
Edit: assuming you meant what you said, please confirm you reinstalled bootmii using the hackmii installer as per the previous step(s). Also confirm how you are trying to launch bootmii