the official "elf-loader" instructions are in the software downloads section of this site (i.e. not with the other documentation but with the O/S files).
I had to use them about six months ago, & provided you follow them to the letter, they work very well. however, if you are using a mac & zterm, there is that one line missing about files>transfer convert I mentioned….
it is a weird experience talking to the octopus over a serial link…