How to play custom NSMB levels on Wii?
I recommend (especially for Homebrew related things such as ROM hacks) that you do not follow video guides. Homebrew scenes are constantly changing with new methods being created over time and video guides become outdated quickly. Instead, it is recommended to follow written guides as these are often updated more frequently and will immediatley reflect new changes (instead of a video guide, which will require the uploader to add in a new link to the old video).
As taken from smwcentral.net:
In order for Riivolution to know which games you would like to modify, you need to specify Patch Templates. These templates are .xml files that you need to place on your SD card. Obviously, we need to get our hands on one of those patch templates for the game we're about to hack: New Super Mario Bros. Wii. Make a folder called riivolution in your SD card's root folder, and place the .xml file you just downloaded in there. Now make a folder called nsmb in your SD's card root folder. This will be the folder where you store files from the game to temporarily replace them.
If you open up the .xml file, you will notice a bunch of code in there. This code decides the section the hack is in, the name of the hack, whether the hack should be enabled or disabled and where the files are located, which is where Riivolution will take your files from.
<section name='Testing'>
<option name='/NSMB Replacement'>This code decides the name of your hack. This name will appear on Riivolution when you insert the game disc into your Wii.
<choice name='Enabled'>This code decides the current state of your hack. If set to Enabled, the files on your SD card will be used instead of the original game files. If set to Disabled, the game will run with all its default files.
<patch id='nsmbfolder' />This code sets the path of your custom content. Down below the .xml file it specifies the actual path where all the files will be stored. Riivolution will only look for files in that folder.
<patch id='nsmbfolder'> <folder external='/nsmb' recursive='false' /><folder external='/nsmb' disc='/' /> </patch>This means that all your files have to be put into the nsmb/ folder that has earlier been explained in the tutorial.
So just set up an xml file in the Riivolution folder as described in the guide and put your .arc file in the appropriate folder (sdmc://riivolution/<mod folder>/Stages/01-01.arc). Just a quick note, this will OVERWRITE the 1-1 stage when you boot your hack in Riivolution.