The NNID can be created the first time you access the eShop. I don't think it matters if you do it before or after you install CFW. The NNID is your eShop account which is tied to the console, and which your purchases are saved to.Confused about when exactly to create my NNID for the first time on brand new N3DSXL. Should I do it on my 3DS *before* I follow the 3ds.guide or *after*. I've never had a Nintendo system that needed a NNID so I've never had one and would like to use the eShop legitimately. Finding conflicting info in researching, whether to put it on the sysNAND or emuNAND and can't seem to find it referenced in the guide.
Do note that you run the risk of being banned from playing online games by installing CFW.