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 click 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 by 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 AUTH.md authentication process.