Get the key for LUKS/dm-crypt from any one of several possible sources (e.g. USB, Passphrase)
makeandmake install(the latter as root)- Copy the example files from the
docdirectory and change them to meet Your setup (descriptions are in the example files) - Generate a new initrd with
update-initramfs -u(as root) - That's it! It should work now!