You can find a detailed explanation of the full authentication process with examples in our github API directory: https://github.com/coinfloor/API/blob/master/AUTH.md
If you run into trouble with the elliptic curve based signing part of the authentication process, please go to here: https://github.com/coinfloor/libecp/blob/master/README.md
We have made a C program called sign_secp224k1. You should be able to compile it on OS X or Linux just be downloading the libecp repository and typing:
Full instructions on how to compile and use it are in this repository as well. Once compiled, you should be able to use it to perform the possibly challenging step of the AUTH.md authentication process.