@Kelzanelie: Kudos for being in the right thread on your first post

.
The process is slightly trickier than that when starting from newish firmwares, check the quote/link in the first message on the 2nd page of this very same thread for a workaround

. (And see you in the dev corner for the gory details on the whole CM+Calibre thing).
EDIT: Aaaand I can't read. You did follow the link. Instead of following the link right away, follow the *quote* to land on the original thread (click on the little blue corner thingy in the top-right of the quote block). This one's in english, and with more details, and provides another workaround if the device is jailbroken.