The best tutorial i can find is easy to understand and I would do it, but the problem is that I dont have a (normal) sd card adaptor
I only have one kinda like this: Although i remember having a normal one inside one of my broken consoles though its at my dad's house
or if it still works since I recall the micro sd stopping working after my dsi stopped working (or maybe it happenned vice versa)
Get a laptop, could be low-spec or whatever. As long as it downloads and transfers files to your SD card.