Installing your theme - suchmememanyskill/SwitchThemeGuide GitHub Wiki

Now that you have your injected .szs files, it's time to make the magic happen. This will require a cfw that supports layeredfs (Atmosphere, ReiNX or SX OS (v2.0 or higher))

To start off, make a folder called 0100000000001000 . In this folder make a file called fsmitm.flag (this file is required for layeredfs for nand redirection magic). After this, make a folder called romfs. Inside this romfs folder, make a folder called lyt. Inside this lyt folder, place your injected .szs files inside this lyt folder.

You now should have the file structure ready. go to your switch sd card and place this 0100000000001000 folder in (cfw)/titles. (for example for Atmosphere this would be in atmosphere/titles). Now load your cfw with layeredfs.

👏 You're done. Now if your switch boots, you should see a beautiful custom background (+ possibly layout) 👏