ELI5: how to get custom themes on my 3ds

[pavo]

so this is my first time ever attempting to do anything "unofficial" with a gaming system. i'd like to put some custom themes on my 3ds, preferably in the simplest way possible, can someone walk me through it? it doesn't have anything that can't be downloaded in the e-shop on it thus far. i read a couple other tutorials on here but i just really want to make sure i don't mess anything up since this is my only 3ds and if i screw it up i can't get another one/get it fixed for a while. like i said i'm completely new to this so thank you guys for your patience!!

 

[BaamAlex]

Follow this guide. There is everything you want to know about hacking the 3ds system.

 

[godreborn]

you can either install cia themes or use anemone. however, I think cia themes disappear if they're fake if you go to the eshop. I've never tried it that I can think of.