1) Download AKAIO 1.8.8 from
here, then extract it to the root. There should be _aio, akmenu4.nds, and maybe another folder, but I'm blanking right now. KEEP THIS ARCHIVE FOR LATER.
2) Get the 3DS/DSi update file
here, extract it to your MicroSD (I just do it to my root to avoid confusion, although I don't know if that's necessary), and run the update file corresponding to the DS the AK2i
is currently in. Once it's done updating, use the power switch to
fully shut down the DS, i.e. hold down the power button on a DSi!
3) Either get the newest loader
here and extract it to "_aio/loaders" or use AKAIO's Wi-Fi Update feature to automatically get the latest loader online.
If you updated the AK2i seemingly successfully (i.e. the DORASU icon shows up on the DSi Menu), but you get a black screen once you load the AK2i, you have run into a fairly common issue. Simple fix: You know that AKAIO archive you kept from earlier? Just re-extract the contents to the MicroSD root, replacing everything it asks to. You should then be good to go!
Sorry, I would have gotten this posted sooner, but GBAtemp started giving me a "502 Bad Gateway" error.