How do I add more storage to my iPod nano?

It's not possible to add more storage.

If your problem is that you have more music in your library than you can fit on your iPod, there is a method for managing this. If you would like more detail, please let us know.

If that is not the issue, please provide more detail of what you are trying to address.

First of all, What generation do you have? Second of all, you technically can, but it’s extremely hard. You have to take it apart and do a lot of soldering with the logic board. You have to get something with higher storage and very carefully solder it to the board. You would have a very high risk of breaking it. It’s not worth doing unless you’re a professional. But, have you ever seen the option to compress your music? If you have music with higher bit rate, you can make it so it compresses it for 128kbps on the iPod.