(You need to have downgraded your mset to 6.x or rxTools won't boot from the DS Profile)
After you copy the files to the 3DS's SD you can run the 3DS browser and visit
http://dukesrg.github.io/?mset/rxinstaller.bin
OR hit L+R on the home menu and scan this QR code:
The bottom screen will glitch a bit, then you hit home (or try to close the browser) and wait until it shows a message saying "an error has occurred".
Then you reboot the 3DS (not always necessary, but it usually does not work for me if I don't reboot)