kk so the first thing you need is dolphin duh
find it here

next you need to setup dolphin to get it running at a decent speed look here
what i did was edit a setting then let NSMBW run on the title screen if it was faster i left that setting on if it was slower i turned it back off and moved to the next setting
NSMBW and the system menu run at 100% speed on my pc

kk once you have it running at a good speed we can start on theming
grab a system menu wad from NSUD or ModMii

in dolphin go to tools then install wii menu select the system wad once its finished doing that you must restart dolphin to load the system menu

now you need thememii
go to options then change nand backup path
set it to \Dolphin\User\Wii\

now your ready to test themes
load a mym in to thememii and use tools then install theme to nand backup
then in dolphin go to tools then load wii menu

NOW HERES THE ONLY PROBLEM
dolphin cant load full themes the app file is just to big so you can only test sections of a theme at a time
then when you have all how you like combine the myms to make one theme this is how i made the Wii OS theme
also the settings page where you set the time and Internet options doesn't work in dolphin

i know it sounds a pain but once its setup it makes testing parts of a theme much faster

thanks!!! Very helpful theming should be much easier now

thanks so much for this Diddy. I was looking how to do this.

VGM out...

Brilliant. I had no idea this was possible. I just grabbed the latest build of Dolphin r7128 and SMv290 (3.2E) from NUSD and now I can test channels at work. My crummy laptop only runs it at 50% though!

Thanks!